My friend with benefits have been telling everyone everything that we do...

He was so freaking nice to me. He always told me that I was a nice person and that he would never hurt me, that he isn't the type of guy that kiss and tell. At first it was magical I would never ask for a better FWB, but then one day he told me that if I ever wanted to be in a relationship with him I just had to told him and we would do something about it. I kinda laugh because I didn't thought that he was serious and then I told him "don't worry I seriously don't want a relationship. Not now and not soon." A few days went by and I realize that he told everyone about what we did. When I confronted him he told me that it was probably that someone saw us and that's why people know that we have something. Later on I find out that they knew things that only me and him knew, I told him how they knew about it and he gave me some excuse that makes no sense. I put in an end and haven't spoke to him after that.
I'm kinda confused because he was such a nice guy and he told me that he telling people about us made no sense because it would jeopardize our relationship and he didn't wanted to finish what we've been doing. 
But again.. There is no way the other people would know about certain things. Maybe someone went through his messages and that's how they know??? Or he was mad because he wanted something serious and I didn't. I don't know. 
Should I trust him or should I end it?