He's never around and doesn't communicate

I've been seeing my boyfriend for close to six months now. The problem is that this guy is always busy and has failed to fit me into his schedule.

I've asked him repeatedly if there is a way we can work around his schedule to see each other in vain. He says he can't give me any time as he doesn't know when he'll have time off. What this means is that he can only see me on his terms and I must fit into his life, no questions asked.

He also doesn't communicate; when I'm not with him I'll be very lucky to receive a call or text message from him. It's always I who calls him.

He's a doctor and possibly has long working hours but I cannot understand how he can't find five minutes in his day to text.

I feel like I'm not getting anything from him, like I'm investing everything and he's reaping the benefits. I get the feeling that he really likes me, but is it enough?

Are those moments worth waiting for if? I feel so utterly isolated and lonely when I don't see or hear from him for days at times?

Am I being irrational? Or are there some truths to my fears?

Liz