Trusting People

My mom used to have an ex boyfriend who she previously dated before I was born. After my mom broke up with one guy, she went to him. This guy was nice to me and my siblings, took me to amusement parks, sent me birthday cards and did all the caring stuff. 
But, idk if he ever sexually abused me. I never had a weird hate for him or felt uncomfortable. He barely even touch me and only hugged me when leaving or to greet me. He would never rub me or talk sexually to me or anything. 
My young 10 year old brain had a very traumatic experience when he left after my mom and him broke up. He was the first male figure I had and first person I had who I was actually really close to. He was all of a sudden saying that he was never coming back and I was broken after that. I just remember crying for days and being very numb. No one explained to me why he left, but he just was gone and never coming back. 
So I stopped trusting people and then eventually started trusting people who I thought would be good to trust. Then they betray my trust and hurt me even more so I end up not trusting people anymore for a long time. Then recently tried trusting my ex, but then after 3 years of being with him he betrays my trust completely and then another friend does the same thing another 3 years later. 
So, right now Im just not trusting anyone and am just slowly tryin to trust my bf and one other good friend of mine.