Im so inscure. Advice please?

So im going to start off by saying i trust my bf but im just really inscure. Im always afraid that hes going to cheat on me or meet someone better and leave me. i never suspected him of cheating but sometimes it runs through my mind. He doesnt really party but when he does go to a party im always afraid that hes gonna cheat or something. He sometimes reassures me and tells me that im the only one and that he doesnt want to cheat on me. Idk i think im like this because he lives about an hour away and we only see each other like once or twice a week so it would be easy for him to cheat because we dont really see each other as often and dont have the same group of friends. I also think im like this because ive been exposed to cheating ever since i was a kid all my aunts and uncles at least cheated on there SO at least once. And im just afraid that im going to get cheated on.

How can i get over this?