I’ve been with my boyfriend for a year and a half, as far as I know he has never cheated on me and I have never cheated on him.
BUT, I guess i’m really insecure or something and I get very very paranoid whenever he goes out drinking and partying.
I think I have a right to be paranoid, but is there anything I can do to help our situation? I’m not sure if i trust him.
I want to trust him fully.

Tell him you feel uncomfortable with it. And find a compromise about it. Maybe you could come with him or come home a little earlier?
Whatever works for you guys.
This situation is very common, esp if you had some else like a parents,sibling or even a friend that you trusted and they hurt you in some way. Its something that takes time to get over with, its ok to be paranoid, it shows that you do care about the other person.
Im like that with my bf and we’ve been together a year and 8 months, its something that will just take time and you cant just learn to trust him because your mind or soul just wont let that happen. I know it sucks right now, but maybe you should just talk to him about it. Tell him how you feel and maybe he’ll turn around and let you party with him or show you that he isnt cheating on you or that he never has.