So my fiance started to dislike sex a couple years into our relationship. She insists it's nothing that I'm doing. I found out in the beginning of July she had been cheating on me from March all the way through June. I love this girl with everything I have so I forgave her, but this just solidified in my mind that it has to be something I'm doing. She tells me she doesn't want to have sex because she's in pain but all I can think is "well that didn't stop you hooking up with him multiple times a week". I shouldn't feel that way. I don't want to feel that way, but that's the reality. We recently decided we wanted to try to have a baby. The first month that she tracked her ovulation we had sex nearly each day. Now it's the second month and we've done it the first day and that's it(now on the fourth day of ovulation). I feel like she doesn't want to be with me or she just flat out doesn't find me attractive anymore. In between last month's ovulation cycle and this month's, we had sex twice. I'm not saying I need it every day, but as a man in his early 20s it would be nice to have sex with my fiance at least once a week. My sex drive is going fucking crazy! I would never even think about cheating on her. That's why I'm racking my brain so hard trying to figure out how to fix this. I can't imagine having a baby or getting married will change this issue for the better. If anything we'll start having sex even less and I don't think I could do that. I ask if she thinks we'll just stop having sex after having a baby and I'm accused of only wanting a baby to have sex, which couldn't be more ridiculous. Ya, I'm making an enormous life decision based on whether I can get my dick wet or not.... It hurt pretty bad that she would say that but I'll get over it. I guess I'm just looking for some advice and a place to vent all of this out. I love my fiance more than anything. I want to have a family with her and be with her, but I don't want to be a miserable dick before I turn 30 either. It feels like that's inevitable no matter what I do. I've even looked into whether I can have my penis surgically reduced because she tells me it's too big and hurts sometimes. I just really don't think I'm that big, but I would do that for her if it meant making our sex life better. Anyone who says sex isn't important is just a liar. I'm not saying it's the most important thing or even in the top three, but that connection you get with sex is important for a healthy relationship. I don't know what I'm really asking here. If anyone has any advice I would be happy to hear it.

Edit: I've been with her for 4 years.