There are a number of avenues you could pursue in relation to combating this problem, but first you need to ask yourself a couple of questions, and perhaps take some quiet introspection. Firstly and most importantly in this situation is do you truly love your boyfriend? If you do, then it's a no brainer; You should stay with him, why risk ruining what you have over what may be a fleeting infatuation. Just because you have a crush on someone else, doesn't necessarily mean you have to act on it. It is perfectly natural to find other people besides your boyfriend attractive, this isn't something you should feel guilty about, everyone does it.
So what are the options available? Well, if you love your boyfriend and want to stay with him, perhaps try injecting a bit of spice into your relationship; this doesn't have to be anything kinky, after all it may just be the initial spontaneity and excitement at the beginning of a relationship that you're pining for, as opposed to another person entirely. If you find that you don't love your boyfriend and that you would rather be with your crush instead, then break it off with him. This will minimise the pain and hurt caused in the long run, whereas if you have an affair then you can probably add feelings of humiliation and bitterness into the equation for him, and possibly guilt and self-loathing for you. If you want to be with someone else, then that's entirely up to you and no-one should judge you for that; staying with someone you don't want to be with will only foster resentment. Most importantly make sure you know what it is you want in yourself before taking any actions that you may later regret.
So what are the options available? Well, if you love your boyfriend and want to stay with him, perhaps try injecting a bit of spice into your relationship; this doesn't have to be anything kinky, after all it may just be the initial spontaneity and excitement at the beginning of a relationship that you're pining for, as opposed to another person entirely. If you find that you don't love your boyfriend and that you would rather be with your crush instead, then break it off with him. This will minimise the pain and hurt caused in the long run, whereas if you have an affair then you can probably add feelings of humiliation and bitterness into the equation for him, and possibly guilt and self-loathing for you. If you want to be with someone else, then that's entirely up to you and no-one should judge you for that; staying with someone you don't want to be with will only foster resentment. Most importantly make sure you know what it is you want in yourself before taking any actions that you may later regret.