Help! Advice!?

So damn. I've been with my boyfriend for over 3 years and it'd be extremely hard to explain all the lil details and ins n outs of this relationship but I will try my hardest to ask the specific question. So basically we've kinda known eachother since we were little I'd say like elementary school and we didn't start actually talking until the end of highschool (because we went to different schools n such) but I feel really weird about him liking all the girls that he's liked lmfao... Maybe because I know them and also know of them. Have even found a bunch of folders on his computer of like saved profile pictures to jerk off to (I could only assume lol) and its just way weird for me but yet I've still put up with it... It may just come down to me being insecure and weird since he's my first real deal bf and stuff. But idk thanks for reading this if ya did. Some insight might be nice!!! Some confidence tips or some shit might be helpful as well because ya bitch feels hella inadequate.