I wouldn't say it's the best idea, but sometimes women don't always make the best choices. I've been guilty of it. I think the question you need to ask yourself is, "Why do we keep breaking up/separating in the first place?" There is obviously a reason why you all cannot stay together, something has to be wrong with the relationship. Just be sure he is not using you for sex and make sure you are okay with the way things are. If this isn't your ideal situation then get out of it.
But hey, I get it, it's hard to get over guys and sometimes there is just that one that does i for you. Be strong and if you think you should move on from him, as I assume you do since you think it might be bad, then move on. Good luck!