Will he stray again??

I’ve been in a long distance relationship for 3 months. We are both in love. But Im still having doubts. We get on well and have lots in common but always had the same disagreement. The big negative in our relationship is the distance. We tried to be friends (his idea) but it failed and only lasted a few days. Simply, because we are madly in love and cant leave each other alone. About a month ago, he was asked to go out with another girl despite loving me. He waited one week to tell me that and I was completely heartbroken even though I knew he had been acting strange over those few days. He admitted he had spend time with her and wanted to go out with her and he said he would normally say yes but didn’t because of me. After an hour ,he said he had blown her out of proportion and concluded it was just the closeness he craved and he’d wait for me. Lately, we’ve gotten closer and Id like to think stronger, but Im afraid I to trust him completely. Im having doubts and Im afraid he’s going to let me go again. Ever since that night , I feel as if he’s ripped something out or had left a bruise that wont heal for sometime. Last night, a month later, I thought about it and couldn’t stop crying. Finally, the tears I had bottled up, spilled over. I know he loves me…but why does the question : “If he loved you, why consider another girl?” keep popping up in my head? I need some advice.