Is my boyfriend lying?

I went out of town the last two weekends, and it was the first time I didn't see my boyfriend for 4 days at a time. To my surprise, he didn't initiate the calls the first weekend while I was away, and he never picked up my calls on Saturday night when I tried multiple times. On Sunday morning, he told me he left his cellphone in car charging. I complained to him and asked him to call me in the future. So when I went out of town again this past weekend, he called. But while I was away from him, my gut just kept telling me something happened the other weekend, there was a reason he didn't pick up the calls, on Saturday night, but he will never tell me the truth and I will never find out why. Even if what he said was true, the fact that he didn't want to stay connected everyday while I was away is not comforting to me either.

I don't know if I can overcome this trusting issue. We have been dating for 6 months, everything was great except sex, he is not very interested in sex. I had to wonder if he has someone else on the side??

This insecurity feeling is really bad. I don't want to feel insecure in a relationship. I'd rather have no one than worrying about what/where he is up to. Should I wait and see and then make a decision? Or just cut it short and call it an end? Any suggestions/tips?