Appreciate the replies, thanks!
No, he has never given me any reason not to trust him, he's never hurt me in the past or anything. I just don't think I'm good enough for him, maybe I think he'll find someone better? Because trust really isn't an issue here, I know he wouldn't do anything. We are always together, so when he's out with his friends he likes to be with his friends. I understand that completely.
I've tried talking to him about this before and he doesn't understand why I feel this way either. He thinks I'm being stupid that he isn't going to find anyone better than me, which is nice to hear, but maybe it's the girls I don't trust?
Yes we are 19 and it is summer so if a night out is planned he will get a txt. We aren't huge fans of going clubbing cause we aren't big drinkers and we both prefer to just stay at home but thing is, he moved school at the start of september so he didn't stay as close to his friends, so when he gets an invite, most of the time he wants to go. I'm happy that he's becoming close to his friends again, absolutely delighted and I'm glad he goes out with them, but theres just something about it that I don't like?
But honestly, I trust him. It's just an odd situation really!
Thanks again for the replies!