Help.

My bf and I have been dating for a month so far long distance. So once i got in trouble and my mom took my phone for a week so i couldn't talk to him when i got it back he was mad at me and the told me he talked to another girl while i was gone. We are still together but this time i have a bad feeling he did it again even though we hadn't talked for and day and a half mow he won't respond to me period. I don't want to blow up his phone but i also dont want to be surprised when he tells me he.is messing with another girl.what should i do?