Well, the one major problem most will have with such spells is the fact that you are attempting to remove "free will". However, there are ways to alter a person's mind, and most don't involve magic. Magic is rarely as blunt as what you're asking. Light a candle, send out your intentions and he magically loses all desire in other women? There's a chance he might come to a sudden revelation that you are the only woman for him, but dare you to take that chance?
So, on to the point at hand! You wish to prevent your man from cheating, or get him to love you instead of any other girl he might be courting? Trying to monitor him 24/7 could easily ruin your relationship, so you are looking to find a way to prevent needing to worry at all. I can think of a few ways.
First, try the non-magical way. Talking... it does wonders for relationships and with it, you can openly draw the lines in the sand. Failing that, consider 5-10 years in the future as well as the present. Selfishness is its own poison and unless they are willingly in love with you then you should avoid the harm you will do to yourself.
Second, while I do not recommend it you can attempt to bind them to you. Throw in a few wards/enchantments and you can start to alter their life to either make them love you, hate you, or go crazy. While I am not overly experienced in this type of magic I suppose charging your intentions into knots might work. Once you have them being drawn to you, you should learn to place wards or enchantments on them. These should be intended to make him unattractive to other women and maybe even repel them. Combine this with the power of suggestion and regular conversation and you might be able to get your favorite man glued to your side.
Has your significant other made any inclinations that he might be disloyal? If so, then perhaps you're in a toxic relationship. If he has not, then it's possible you're contributing to creating a toxic relationship. The most powerful form of magic, in any interpersonal relationship is communication. It will go a lot further than etching his name on an anointed black candle; which, I'm skeptical at best will do anything.