How can I trust my husband again

A text popped up on my husband computer and I found these. We are very open with passwords and such so I went to this phrendly website to check it out and he had an account linked to his email.

The day he created it he was on a 24 hour duty at work (staff duty- he sits and makes sure nothing goes bad in the barracks). He only has to do these once in a while. I couldn’t find any messages on the account but I know they had previously talked on there because she was replying to her last message. You can “like” girls on here and this is the only one he liked. He had no photo and nothing else I could see about him looking for others to talk to. I was really upset when I found this and when I confronted him he said he was just bored at work... but he said he stopped after like 5 minutes because he knew it was wrong. I don’t think the conversation could have gotten out of hand in a short period of time.

I did forgive him but told him if it happens again I’m out, no matter if the convo is innocent because married men shouldn’t be on sites like this. I feel like he disrespected me and I’m having a hard time with my self confidence seen I found these.

Now I’m constantly wondering what he’s doing and if he’s getting on more sites. I asked if there was something I wasn’t full-filling in our relationship and that’s why he did it but he says there’s nothing. I thought we were in a great place but then this happened.. I just want advise on how to get over it and trust him again, because right now I’m having a very hard time.