Past relationships ruining my current one?

So I'm 25, and engaged to a wonderful guy. We met in highschool and lost touch and reconnected last year and realized we should of been together all this time. (We had a crush on each other in highschool but were too shy so dated other people) and he's been great to me the whole relationship, but in just about every other relationship I've been in I've been lied too and cheated on, and although he hasn't given me a reason to think so I'm afraid he either is cheating or will cheat on me. Hes lived with me since the beginning due to life just being a bitch, and he's never out, he's never late from work without a legit reason, he let me know the password on his phone but I don't want to be THAT girlfriend, especially since I have no real reason to think he's cheating.

I'm just wondering if this fear will go away or if I'm gonna be worried my whole life that I'm gonna lose him too...