I know why. It's simple. You're still in love with him. There's nothing wrong with that, there has to be good things about him and good times you shared, but realistically you have to stop and think now if it's really these memories that you love or what you have now in front of you. Many people make the mistake of staying with someone because they think love will overcome all in the end, that's simply a lie. When you love someone, I mean really love them, you don't hurt them you want to protect them, you don't belittle them, you want to build them up, make them feel as special as they make you feel, you want to be with them and enjoy the time you have together, not get annoyed and frustrated when they gate crash at all hours, disrespect your sleep patterns or that you have to work or have exams etc the next morning - quite simply you don't hurt someone you love - if you can at all help it. And when it does happen (we all make mistakes) you feel so bad you'll do anything to make things right again, you don't start with name calling, emotional blackmail, or worse. Sometimes even with the best of intentions some problems can never be fixed, and regardless what you hear, time heals nothing, forgiveness (real sincere not begrudging words you say cause you think you have to) real forgiveness does heal things. You have to learn to be a little bit patient.
You will always have feelings for him whether he was mean or loving because for whatever reason he is who you fell in love with. Take a good hard look at what you fell in love with and what you see when you look in his eyes now and PAY ATTENTION to the gut feeling you get from it. Remember never stay with someone when everything inside you or external influences think you should, no one was ever born on this earth to be taken as another's slave - unless that's the path YOU WANT to take.
And don't give yourself a hard time over feeling so miserable and mixed up. You're suffering, it's called a broken heart for a reason. You're mourning what was not what is. If you were looking at the pain and arguements and tension of the last few weeks from another's perspective (and maybe you'll be able to see this in time) then you'll reaslise what you're upset about isn't the end of your relationship, if that's where you choose to take it. More than likely you'll be happy to get out of that drama, but it won't stop you wishing things had been different or the way they were before. And beware of anyone that promsies to make things go back to the way they were before. Nothing ever stays the same, and nor should it, even happy moments are tinged with sadness as it should be, without them you wouldn't get the rollercoaster of emotions that you get when you're in the arms of someone that means the world to you. But if there's more bad times than good, if you want what was more than what you have you need to wake up to yourself. Everything evolves, even love grows. So does anger and resentment. As you grow as a couple you will grow away from that blossoming start into maturity, anyone that wantsto keep going back to the start will be doomed to repeat the same old mistakes and not learn a **** thing from them. In that case, get out or take responsibility for what you end up with.
Just don't allow yourself to be blinded by empty promises or threats of intimidation - you CAN get by without him, you did before he came along, and you will continue to do so. Same as him. If things calm down and you meet up again and want to address the things that cause you the pain right now then good, you might get some answers then - you might not too. It's possible he's feeling as mixed up as you are right now, and it won't be until you both take a big step back and really have a long hard think about what you both want and where you want to be in this relationship that things will start making sense between you... Be aware that you may never get any closure. Sometimes things just are the way they are, and that's it. Don't fret so much over the details, you'll drive yourself mad chasing answers he can't as yet give you. If you hound him you'll only succeed in pushing him further away and you will just end up with more heartache.
Give him and you some much needed space and accept the pain as a part of your relationship. It hurts because it's meant to. If it didn't hurt now it would mean you never really loved him in the first place
*hugs* Chin up.
You know where we are here should you need us.