A couple of years ago my OH and I swung quite a bit. Over time we naturally progressed to going full swing, or at least attempting to.
On two separate occasions (the only two occasions actually) we've gone for the full swap. Everything was fine with me mechanically so to speak, until we put the condom on. Then... nothing. It just went 
We tried to work it out at the time, but just couldn't. The woman I was about to be with was very attractive (a different couple each time), I didn't feel anxious or stressed/tired etc, my OH was enjoying herself with the man of the couple and I was enjoying that she was enjoying herself.
The first time it was a bit embarrassing and awkward, and we didn't really discuss it with the other couple (and I felt that she'd taken offence shortly after). The second couple were more experienced than us and understanding. They put it down to me concentrating on my OH, making sure she was happy - but to be honest I was completely in the moment at the time.
Since then life has got in the way, so we've not had time to meet more people. The thing is, now life is leaving us alone were thinking of getting back into it.
I'm a bit concerned we'll get all revved up and then I'll have another failure, for no apparent reason. My OH and I very, very use a condom between ourselves, and then it's only if it's anal and she's concerned she might not be 100% clean.
Does anybody have any advice on how to hopefully avoid another failure if we swing in the future?
I had a partner once who lost an erection almost every time he put on a condom. It was very frustrating for us both, but with a lot of time patience and practice he managed to get to a point where he could become erect again shortly after putting the condom on. I can't really comment on the specific swinging situation, but perhaps you could buy a big box of condoms and practice using them with your partner or even whilst masturbating to get used to them being involved in sexual situations? Perhaps then you'll keep your confidence whilst swinging :) hope this is helpful
I've only ever been with one person and I've lost erections before as soon as the condom went on, so this is deffinitely a thing. Me and wife have only ever slept with each other and she's on the pill so I haven't even had to try and use one in many years.
I think the best bet is to start using them regularly during sex with your OH and hopefully you'll just get used to it. A cock ring is a good suggestion, too.
If all else fails; use something else (fingers, tongue, toys)! We're all human and sometimes our bodies just don't cooperate with us. I'm sure your partner will appreciate you not making a big deal of it and just adapting and going with the flow, etc.
Good luck (and have fun!) 
I've had another thought, if once you've practiced with condoms with your partner keeping an erection whilst wearing a condom is still difficult, may be you could ask potential swinging partners if they'd be happy wearing a femdom? That way you're being safe and not having to wear one yourself. I agree cock rings are a good thing to try too.
Do you think maybe it could be a psychological thing ? You say you're up for a full swap but maybe there's a tiny part of you thats holding back and thats triggered as soon as you start to put on the condom .
You could try to use condoms regularly with your OH so you get used to the feeling of them more often .
Hope I haven't offended you with this ,after all you know your mind better than all of us on here :)
If it is the condom that's the issue then my suggestion is to get it on as quick as you can in one motion and then get to it, you'll soon pick up. Get the other person to help you along too.
Practising the technique is also important and you might need to check that you've got the right size because if you're bigger than average then you'll find it very difficult to "roll" one on and might find they split or are at least far too tight, which can lead to problems like that. If so then try skyn large as they are both larger and yet still thin.
If it's actually an emotional/psychological response then that is a different story and one which you might need to consider carefully with your OH.
I'd agree with a lot of others and check the condom dude if things. Making sure a good fit is key, and so many manufacturers do a range of sizes now if you need too try something other than a standard fit. MySize do a measuring guide which while it's designed for their range, if might help identify if you fall into a non standard bracket.
I often find getting my OH to put the condom on helps with keeping an erection, and if I begin to lose it she's in a perfect position to rouse him back to life.
On the physiological side, maybe worth having a think and making sure you and your partner are 100% into this. Wildflower made a good point, is it possible there is a little something holding you back?
Thanks for all the advice guys 
Weve been together for 7 years and not used condoms for 6 1/2 of those, so I reckon it's because I'm not used to them. We tried the other week for anal and the same thing happened. We'll definitely be using them to see if not being used to them.
We're both certain it's not physiological as it's something we both really want to do. I'm always erect during oral with other women and it stays right up to the condom going on. If we remove it, it'll come straight back!
I'll take a look at MySize. My girth is larger than the average, and I do sometime find I'm left with a ring around me where the opening has been... Always ignored it, but it could be an issue I guess. Never really considered myself to be a 'big boy' so to speak!
Do you think maybe it could be a psychological thing ? You say you're up for a full swap but maybe there's a tiny part of you thats holding back and thats triggered as soon as you start to put on the condom .
You could try to use condoms regularly with your OH so you get used to the feeling of them more often .
Hope I haven't offended you with this ,after all you know your mind better than all of us on here :)
Hi Wildflower,
It'd take an awful lot more than that to offend me! 
We checked our most recently purchased condoms, and they had a 52mm nominal width (which is smaller than the ones we usually buy) no wonder they were almost cutting my c**k off! 
We then bought some regular Durex ones with a 56mm nominal width, with the same effect.
So I the found a site (which I'll shortly be adding to the pander to me thread!) where you measure yourself and they send you custom fitted (more or less) condoms.
It's been a bloody revelation!!! They go on easily, don't slip or tear and the sensations have been vastly improved! Though obvs still not quite as good as bareback.
i have to say though, when you've been in a relationship for over 7 years and not used condoms for 6 1/2 of those years, it's very, very weird to be using them again. Even though it is only for practice. Using them solo is only slightly less odd for me personally as well.
We're both very happy and now hoping to try the whole swinging scene again with more success!