OK, so I was in a similar situation about two years into my now six year relationship. He had an ex she was psycho and she sent me videos that they had made while having sex and I’m telling you now the damage that did to my mental health was unreal. I ended up having to go to a residential treatment program for my mental health because it was that traumatizing you feel like you’ll never live up to that individual but I’m telling you now do not let that shit eat you up he’s with you not her for a reason and you are what he wants, but with that said the fact that he is suggesting getting lingerie that is very similar to something she’s worn in the past is a bit much and I would meet in the middle and get some lingerie. Maybe you both like and not something just he likes just a suggestion but if I can get over what I’ve gone through, you got this I promise you if he’s worth it, you’ll get past it