Need help: Fears of my Boyfriend leaving me for another girl?

So I've been in a relationship with this guy for almost 8 months now. He's kind, he always says sorry when he thinks he's upset me, he's always telling me he loves me, and being patient with me when I'm down Ill and can't really get out of bed(I'm very weak most of the time) and we often fall asleep talking to one another over the phone. True, he has a flaw, when we play this online game we both enjoy he will sometimes get stressed and snap, but as soon as he does he flips out and starts saying hes so sorry for doing that and that he shouldn't treat the person that's most precious to him that way. But here lately...I've been getting really paranoid and scared...I'm scared hes going to leave me for another girl..that they are better for him and stuff. I can't stand the idea of loosing him but I've been getting really scared he will leave me sooner or later because of me being so weak, or because of the fact i just don't seem to do anything impressive to him anymore..I don't know what to do...I know I should trust him..but because of my last relationship(the guy cheated on me more then 10 times i know, probably more) I'm really scared...