No one is (on this particular post) telling you to leave. They are telling you to take a real long, hard look at what is going on.
As for him being your best friend, he may or may not be. The problem here is not him, it is you~! You are NOT YOUR best friend. I will not say, do not forgive him his errors. I have not read any other posts by you to know what it entails. I will say, if you LOVED yourself enough, you would take care of yourself. Whatever that means to you.
I am sure, due to the past you mention, there is justifiable reasoning for you to be "scared of someone caring" yet it is also sounds as if you have not Found Yourself, your Center. Without that, the other person is always going to have the same characteristics, just a different face, name and body.
I have met the same men over and over again. The only common factor in the equation was ME. I had to stop and look at what I was doing to attract these men. I had to stop and look very hard...AT ME. Believe me, it is, well more precisely, was not pretty OR easy. It has become much better. I have taken responsibility for my life. I have chosen not to live from my past anymore, also. I stopped dating over 2 years ago and am beginning to learn how to put myself back out there. I realized when I thought I wanted to date again, I forgot how...mostly because I had previously made bad choices. It is a learning process for me. All this is said because you (may) need to be by yourself until you learn how to release your past, so it does not continue to be your present. It is a difficult task yet it is necessary.
As for relationships being hard, I so disagree with that. I do agree with Soul, we do have our differences with people and there is a way to disagree. If you cannot find the way to a civil conclusion, then it becomes necessary to agree to disagree. Not always will the other person's belief correspond with mine (yours, or anyone else's). So, rather than beat a dead horse, we will agree to disagree. Yet, to argue, fuss and fight about 'it' (whatever that may be) I will no longer do this to be in a relationship. I do not see that to be with other people (men, in particular, people in general) it is necessary to struggle to keep a relationship going. I have come to the conclusion, I will no longer be in that type of relationship. I will, as soon, be with myself than do that again. OH and as Soul mentions, I will *obviously* find a man with like mindedness to be involved with, from this point on.
It is not to pick on you. You, being young, have more opportunities than to be where it is not healthy for you. Thus, the reasoning behind why people *may* mention you're young, just move on...as opposed to 'being older and forgiving, especially if married'.
As for your apartment, if it doesn't make you happy...move! OR make it more personal to you, where you find comfort in being there.