How to trust?

In September me and my man split.. he wanted to go for a rebound at hit a girl up with the intentions of hitting on her and asking her out. He soon after regretted it and never did anything. He knows I’m giving him trust but I have a hard time. Like I forgive him I’m just still healing. Anyways, two of my good friends knew this and STILL allowed me to fight for my relationship and pushed to save it WITHOUT saying shit. He eventually told me himself before we got back together and I explained how he broke my trust and how I am having a difficult time but I’m healing. I just currently realized how do I know I can trust people, my friends knew and didn’t say shit to me... I’m the only one with a car and license who actually drives legally. I’m normally hit up in emergencies or when we hang out they try and get me to pick them up and get them. WHILE IM ALREADY AT THE DESTINATION. So how can I trust ANYONE. Even the friends I do trust I’m just like how do I know they’re my friends you know? I’m having such a hard time it hurts. I haven’t talked to my therapist about this but I CONSTANTLY every single day think about this. I’m so insecure and scared. Idk what to do. Idk if I’m overthinking this and letting my anxiety get to me or what...