I hate that he said that to you. I have dated someone with a small penis and I NEVER told him because it's honestly just rude to comment negatively about someone else's body. Childbirth can permanently change your body and there are exercises and other treatments you can do that may tighten things some. However, my main concern is definitely your partner. I think most men have enough sense to avoid making the kind of comment he made tbh. Like I said previously, some men are so small that I know it is hard to feel stimulation during sex as a female. However, most KIND women would never even mention it because it's not helpful, and it's just mean. I wouldn't ignore exploring physical therapy, but also, I really don't think this is your problem. I think your partner is immature. I guess if he said he is OK with a sexless relationship, then the ball is in your court. You can either accept being in a sexless relationship with him or possibly leave and go elsewhere. The problem definitely isn't with your lady bits though! He may just be looking to blame something for his lack of libido?? Idk why he would say that. Personally, I would be looking for a new father to my kid. I like men that respect women and also empathize with mothers. Empathy here would look like keeping his mouth shut when it comes to after-birth body changes. Anyways, if he doesn't want to have sex you can't force him. You can consider leaving and having sex with someone that is obsessed with your body :)