What could be going on?

Whenever my SO and I have sex lately, he can’t cum and he gets dizzy and has to stop and his penis and lower body is a bit numb.

This happened last year because of the antidepressants he was on and he got off them but now he’s back on them and his antipsychotics he was on before. He also had trouble getting hard or staying hard then but he’s not having that problem now.

Him not being able to cum started happening again 2 days before he started his meds again so I’m wondering what else it could be. Apart from his meds.

I’m a bit worried because we’re going to be TTC again after I get my period after having a miscarriage last month so we obviously need him to be able to cum