How do I get the mister to trust me?

My boyfriend always thinks I am behaving supisiously and he dosen’t trust me. I ‘ve come to notice this when I began college last year. I would have male study partners and sometimes they would have to call my celluar phone. When they would call I would simply dismiss the calls until he noticed. He was worried but he soon got over it. Then this year I moved on campus to be closer to him. I am now far an hour away from home and I get lonely sometimes and he is not always available [because of work] to keep me company so I made a few friends who live in the dorm as well so I won’t feel so lonely. Now, these friends are guys but they all know each other and me its is kind of a friendship circle but we don’t sit down and chat on the phone or anything but we do have each others phone numbers so if maybe we would like to hang out we could be able to meet each other and play cards or something. The relationships are strictly platonic. However, I was stuck at work oneday and my boyfriend told me he couldn’t come to pick me up so I told him I would find a ride and I did. I called him and told him a male friend from school was coming to pick me up and he got upset. Then he kinda got over it then we [my boyfriend and I] ended up hanging out later that day and my friend who picked me up text me and he got furious. I understand where he is coming from because I wouldn’t like him to have friends of the opposite sex calling, texting, or picking him up but, damn, I needed help and that is what friends are for and after all the relationships are platonic. How can I get him to understand that I have friends but I am not and have never cheated on him when the situation looks so wrong and guilty?