just for the record.
No, it means hes a streight normal male.
Men cheat for two reasons: Either they have lost interest in their woman, or they are starved for some kind of attention (sex, companionship)
If you are afraid he's going to cheat, you first have to confront your insecurity: you are being untrusting and silly in worrying over something that will NOT happen if you are even remotely paying attention. Are we past that yet? good.
To prevent a man from cheating, you need only do to things: tend to his needs and maintain physical attraction.
If he has a need that you are not filling, in his primitive head you must not be the right girl. He'll not only cheat, but you can look foreward to an ugly breakup as he tosses you away, or casualyl forgets you exist. To prevent this pay attention to his complaints and stresses, and act on them when you can. His needs aren't just sexual either. Sometimes it's as simple as keeping him from being lonely.
If you are no longer physically attractive to him then he'll just plain lose interest. At that point you've lost. After all, pretty girls in all shapes and sizes, colors and flavors walk by all day. He'll just pick a new one and move on. To prevent this just pay attention to the girls he flirts with. You don't need to become them, but you do need to capture and understand the trait in them that caused him to flirt. If he sees more things in you that he likes then on the girls passing by then you don't need to worry about casual flirting.
A note, since it'll help. Pay attention to the environment he lives and works in. If you don't fit well into that, how can you expect him to be happy?
That's it. That's all it takes to keep a man from cheating. Men are simple and stupid. A smart girl, should have no problem keeping one.