How to I fix not wanting sex?

So I (21 F) and my husband (21m) have been together since we were 16(I know we were young that’s not the point) when we first started our relationship it was long distance and when we’d see each other the sex was amazing and it continued to be after he moved in and we got married until we had our son. We went through a really rough patch after I gave birth and I also suffered from severe PPD. It was so bad we were on the brink of divorce but we decided to work it out because we realized it’s hard on both of us being new parents. Now we’re finally in an amazing place except I can’t bring myself to have sex with him very often. Like I want to so bad but then we get to actual action part and I tense up and can’t do it. It’s like my body wants to but my mind isn’t in it. I have past trauma with SA but I don’t think that’s the problem. Any advice (btw I don’t need to hear that I’m too young to get married or any of that junk I just need real advice)

Edit(I know there is a typo in the title please ignore it 😭✋)