It's a tricky one. There could be so many things causing her lack of interest in sex. It could be stress, tiredness, hormone problems, fear of pregnancy or body confidence issues, feeling under pressure to perform or so many other reasons.
It can be really difficult to get to the bottom of what's wrong and how you approach it can make all the difference. Sometimes well meant comments about "being sexy" or "wanting to do xyz" can seem like pestering so maybe let her know how much you love her and appreciate her and miss her when you are apart. When you do see her again take her for a meal or go to the movies. Try to do anything fun that doesn't just involve sex like when you first started dating.
As for lingerie do you mean sexy stuff like stockings, suspenders and basques? (I hated wearing these for a while and just felt I looked tarty and it was the last thing I wanted to do was get all dressed up and perform when we were stuck in a rut but now we are back on track I love wearing them again.)
Maybe get her a gift of something pretty rather than sexy to make her feel good about herself. There is some lovely stuff on here like the lace robes and the Lovehoney spoil me satin babydoll sets that would make her feel good without feeling "tarty". There is some gorgeous bodystockings too that are really flattering.
Our sexlife really suffered after having kids. I was shattered even though my OH was a brilliant help with them but when we finally collapsed into bed the last thing I wanted to do was get jiggy. Sex just felt like another chore on the to do list and it got to the stage where I felt wrongly that was all my OH was after when he was nice to me.
It took a long letter, an even longer talk, a back to basics approach focusing on kissing, cuddles and spending time together and enjoying each others company again with no pressure to have sex that got us back on track. Once we got the intimacy and feelings of love back then I started to be more interested in having sex and finding ways to improve things which led to me looking online for tips to bring back the spark and it was then that I discovered Lovehoney and with the help of products I bought from here and advice and tips from other forum members our sexlife has gone from strength to strength.
Good luck :)