What would you do?

I have been with my boyfriend for almost four years now. We had a rough patch this last July but we were starting to do a lot better recently. Yesterday I was looking at a post he showed me on his phone on reddit. While I was looking, I saw that he had reddit messages to 2 random girls from July trying to get to know them. The girls never responded so all it was was his 2 initial messages. When I confronted him he said he was extremely sorry and never planned on actually meeting up with them or doing anything with them. I never in my life imagined that he would do something like this and I don’t know if I should leave or not. What would you do?