I Have Trust Issues

How do you get past being suspicious of everything and everyone? I have been with my fiance for 7 years now, but I still have doubts, or get weird about his online friendships he doesn't talk about, and if someone mentions it he is all "It isn't what it sounds like" or some version of the same. He gets extremely moody if I ever talk to the opposite gender online, but idk. I guess I am just having a weird day and wanted to vent.