Should I stay or should I go?

Four months ago, I went out for brunch, after a crazy night out partying... I was sitting outside on the terrace talking to my friends about everything and nothing, when I noticed this guy sitting with them. A guy I noticed before, but never really paid attention to. This is the day M came into my life. He was good-looking and he was part of that group of people everyone wanted to be friends with. But, following the rule book of seduction, I didn't talk to him... Of course I would give him some glances sometimes and catch his occasional stare... but that's it.

Brunch was over and everyone went home. And when I got to my room, to satisfy my facebook addiction, I had a nice surprise... M added you to his friends. And there was the first step to what should become a relationship. I added him, obviously... but when I saw his profile I was upset... M is in a relationship. I just thought, damn it... I am not a relationship breaker and I don't like guys that cheat. I guess all he'll ever be is a friend. We started chating on MSN, but nothing wild, since I thought he had a girlfriend. He took me out for a drink, nothing happened though. We had a drink and he drove me home and said goodnight. I have to admit, I was kinda disappointed that he didn't even try to kiss me, but all I was thinking is "girlfriend, girlfriend, girlfriend".

And then the best surprise of all, Facebook once again... M is no longer listed as in a relationship. But then I thought, what? But he didn't try to kiss me... Damn it, I'm just a friend it seems.

I proved to be wrong. Friday came and I was prepared to party with my girls, when I got a message... where are you? I'll pick you up, let's hang out. So there he came, all charming and good-looking and picked me up with his red car from the bar where I was getting drunk with the girls. (And for the protocol, two months later I found out he had friends spying on me that night, to see if there were any other boys flying around me). 

He took me back to his place, where his friends embarassed him by making hearts of post-its on his wall and lighting up a dozen of candles. I thought it was cute, he was just totally embarassed. We talked for a looong time... or I talked, most of the time, because I was so nervous.

And then he kissed me. We kissed for hours, and when I told him I wouldn't sleep with him, he was totally fine with it, kissed me, held me in his arms and we fell asleep. I think that's the moment I decided that I should give that guy a chance. I had gotten my heartbroken, but he might just be different. 

We had to wake up early that day, since it was his graduation. We spend every minute of the next night together as well... and than it was already goodbye, because I was leaving for Paris.

He came to visit me... I must say, it was awkward, I still had my guards up and he felt it. But he fought for me... 

I flew to Serbia to see him, and when I saw him at the airport waiting for me I knew... I had totally fallen for him. I flew back to see him again two weeks after that.

We were happy... I was happy. We were great together, apart from the occasional fights that keep a relationship exciting. And the sex was worth waiting...

But now, I don't know what is going wrong... but something definitely is. He doesn't fight for me anymore, he takes me for granted, I can feel it... The: "I'll text/call you tomorrow!"-promises keep getting broken, and I am turning into this pathetic girl that keeps on calling and keeps on texting and keeps on getting upset, mad and angry at the guy for not answering... and he gets annoyed, and I get annoyed... WHAT IS HAPPENING? So now all I want to know, is it just a phase, is he maybe hiding something, does he feel guilty, and does he still love me like he used to?

So tell me.... should I stay or should I go?