He is my colleague and friend and we have been going out for around 8-9 months. I am his senior in office. Earlier we used to text a lot. We used to play table tennis together in office and that is when we became friends. The way he looked at me seemed there was something more than friendship. Then one day he asked me out for movie. Nothing much happened between us on that day. However after few weeks he started calling me during late night hours. We used to talk continuously for 3-4 hours. This still continues. My problem here is that he does all things which indicate that he loves me however he has not yet expressed or said anything which is pissing me off.

We have been going out for almost all weekends till now. Its been a routine that we meet up every weekend and he will take me to some coffee shop and spend time. Our eyes also got locked couple of times when we went out. And I could feel that thing between us. He teases me lot and laughs at every single silly thing that I say.

Also a thing which I do not find OK is he doesn't talk to me much in office. I don't know why?
But then after office he will call me during late hours. I haven't seen him mingling much with my colleagues.
He has 3 friends with whom he goes out for lunch and all. Few months back 2 of the guys in his group left the job and only one of his friend is left. She is a girl. So now they both go out for lunch and tea together.

Initially it was OK however I have been noticing that now they come to office together around the same time. I have noticed this 4-5 times. They were on same project some time back so I could see this girl sitting for hours in his cubicle almost daily. I have also seen them going out together couple of times for tea/coffee.

Initially I was in notion that she is married and recently came to know that she is not. I came to know that she is engaged and will be getting married next year.
Also I don't see this girl getting along with other female or male colleagues in office. She is mostly seen with my friend. One of the reasons which I think could be that my friend and his fiancŽ are college mates and friends. However I am afraid if there is anything going on between my friend and her :(. Is he in love with this girl?

My problem is I don't understand this guy. He likes talking to me , going out with me etc and doesn't confess anything.
What's going on in his mind? Is he doing two timings? I even have asked him no. of times if he is engaged with some one or likes some one but he says no.

Another thing which I is noticed during last 9 months is that all of sudden something happens to him and he will stop talking. He will not tell me anything. And then after 3-4 days he will say sorry for his behaviour. This has happened 3 times during last 3 months. I feel mind ****ed when he does so.

I sort of shouted at him 3 days back since he was not picking up my call and didn't even reply to my messages. And then his cell was showing switched off for 3-4 hours. I also told him that I was worried and didn't had any other number where in I could reach him. He said sorry to me however I felt his behaviour weird. I was getting very different vibes from him as if he is least interested. That's the last time we talked. He hasn't called me yet.

And yes its weird that we haven't talked since last 3 days.

Its my birthday today and even if he does not love me he could have alteast wished me or texted me as a friend. I haven't received any call from him yet or any messages.I will not be surprised if doesn't even know my birthday :(.

Please help me out. What should I do? This behavior of him is driving me crazy and I am already feeling hurt.