Intimacy troubles

I don't know what to do to make mine and husbands sex life better. We have sex maybe 4 times a month... and today I tried talking to him about it and it didn't go so well... he cheated on me 2 years ago. And I made the decision to forgive him and take him back , but lately I've been questioning myself why. I've tried buying lingerie to look and feel sexy for him but he told me not to bother and he's not interested in it. He's 29 and I'm 24. We have been together since I was 18 and he was 22. Today I told him I wished we would work on our intimacy issues and try to attempt at having sex more than 4 times a month. His response was he's old and not young any more. He said with past girls he would have sex twice a day and he doesn't have that stamina in him anymore. I feel like I didn't need to know that especially bc he's not doing that with me. I feel like he doesn't seem that way to want to have sex more.