How Do I Deal With This?

I don’t want hate for this. This is something I’ve personally been dealing with during every relationship and it’s ruining everything. I have tried therapy and nothing is working. I don’t know how to stop myself. I have a habit of looking at my boyfriend’s snap-map on Snapchat and when he was last seen. I know this is terrible and I feel so bad for doing it. I was working today and I just kept on checking it.. He was online like every 2/3 minutes and I blamed him for texting someone else and cheating on me. Again, I feel absolutely awful.. My mind plays tricks on me. I’m being distant with him and I don’t know why, I’m just afraid of being hurt. I’ve been in a toxic relationship in the past and I don’t want to go through this again. How do I deal with this?