Need advice...💔

Little long sorry....Awhile back (around 2 yrs ago) my husband had been sexting his ex and saw in the texts that he stayed the night with her and he said he left and didn't stay but I never found out the truth to that (that's a small part of the whole thing), but anyways we worked through it and made it work out. With being 18 weeks pregnant and having my hormones going crazy the past couple of days all that's been going through my head is remembering reading the texts between the two of them. Seeing things he said to her that he never once had said to me and just not being able to Believe he was talking to another female that way. Remembering the pain I felt going through that. Now I know he wouldn't ever do that again but I'm just remembering it all and my husband can tell something is really bothering me, do I tell him this has been playing through my head? If so how do I tell him that? I don't want him to think I don't trust him I don't want him to feel like I think he's going to do it again because I don't but these thoughts are making me feel so down... I need help! Please