Our experience is different from yours, but you’re not alone! Some of the things that helped us might not be as helpful to you, but thought I’d share 
We were really sexually active earlier in our marriage, but after a decade, we had a period of a few years that we rarely had sex or masturbated. We weren’t having any marital problems, we just weren’t getting sexually intimate. Then when my libido went up and I started wanting to have sex more often (this is about a year and a half or two years ago, early thirties), my husband started having performance anxiety. He’d get hard then go limp when he’d put a condom on, or he’d stay hard to penetrate and then would go limp or would cum right away, like within 20 seconds. We didn’t have any sex toys and weren’t on the forum, so didn’t have a good place to go for advice, so I just started googling things like “going limp when putting a condom on” and “can’t stay hard during sex” and found a bunch of random things to try, so we started trying them, like using different brands of condoms and him masturbating with a condom on. He was really embarrassed to do this because sometimes I’d be sitting there watching him, but I’d try to give him a sexy boob show and praise him (to try to give positive reinforcements to replace negative feelings). Also getting him really hard before penetration instead of starting when he was semi hard but still kinda flexi (not sure how to describe this better). This is when I started giving him blow jobs again because he’d get really hard from that. We had been just jumping right into sex, so just foreplay in general helped him get harder and keep his erection.
After we found out about Lovehoney, he started using cock rings, and that helped a lot, both getting harder and staying hard longer. My having clit vibes to get me to orgasm quicker has taken some of the pressure off of him too as sometimes he’d have to wait quite a while on me before. After he got a Fleshlight, he started trying edging to get better at knowing when to stop before he’d climax. Also lately, trying to be more intimate so that we’re both enjoying sex rather than him feeling like it’s just him giving me the sex I want. He feels like the more often he masturbates or we have sex, the longer he’s able to last, but even still he’ll cum quickly if he’s not mindful about it. He’d rather not have sex than talk to a doctor about it, so I’m really glad to have different experiences and advice to read about here on the forum 
I’m glad that your OH is considerate and understanding of you because I was not very considerate. I took it personally when he’d go limp and would get irritated when he’d cum so quickly. He didn’t tell me until later that he was always really stressed that he’d cum too fast or go limp and disappoint me, so he’d get really anxious every time we’d have sex, and my reactions made it worse. When he finally told me, I kinda had figured that was the case as I had been reading about ed causes on different sites, and I felt like such a crappy wife 
I’ve been trying to make up for it by being more patient and giving now. I feel really dumb writing some of this because some of it is common sense, and a lot of it was my fault, but I can’t change what’s already happened, so trying to keep looking forward.
@FantasticMrFox Hope you find some things to help your situation 
If you haven’t listened to it already, this sexual happiness podcast episode is really good (about premature ejaculation, erectile dysfunction, poor body image, low sexual desire). It was the first one my husband wanted to listen to. It’s interesting that a big part of erection health is psychological, but a healthy lifestyle (exercise, diet, alcohol, smoking) plays a big part too since erections are all about blood flow 