He doesn't call

Help me and post, I saw what you posted the evening, and is similar to my case.

I have been dating this guy for 4months now, he doesn't call me else I call, and each I try to complain he'd tell me his busy and he promises to call back, but won't. But anytime am with him is as though nothing happens the love and attention will be there, but once he's no longer close to me the attention equally drops as well. 

Please guys I need advice could it be there's someone else, am not saying his cheating, as I have not seen any. But his attention is not always with me. Kindly advice.