Should i tell him or not?

So me and this guy been talking for awhile but we’re not official. I live with my husband but we’re not together, for now it’s the only option we got. Also i’m getting to the end of my pregnancy with my husband. So tonight i asked him to put shea butter on my sides to prevent stretch marks n he did he started touching me n stuff then put his dick in i wanted to say no but i just went with it in the moment cause it felt somewhat good. But i feel like my body is rejecting him because literally after he got done i could barely breathe right n felt like o was about to pass out. So anyways i feel horrible because i did what i did n feel like i should tell the other guy because he’s just a really good guy but ig since we never made thing’s official idk if i should actually tell him even tho i feel like i really like him and he likes me but idk what i should do rn