Will I ever stop looking for the Struggle?

My life is improving. I have a wonderful job that I love. I have the support of my family. My mother and I have become extremely close. My daughters are happy and safe, doing the things they need to do to grow up and become successful happy adults. My car is fixed; my dog’s nails are trimmed. The relationship between me and my boyfriend feels safe and caring. Things are truly looking up! But I am looking for the struggle. I am obsessing over him cheating on me a year ago. I thought I had forgiven him. And my heart says that I have but my head says “hell no you haven’t”. The last time he was this nice to me he was cheating on me with his ex girlfriend and various others. So now I am sitting here wondering if he is doing it again. Can you believe that?! I can’t even allow myself to be happy. I am in constant search for the struggle. I am scared because I am aware that these thoughts and feelings are what trigger my downward spiral. I will obsess, then get careless at work, miss days, lose the job, and it just continues from there. My ever so supportive mother tells me I have too much time on my hands. To maybe find another job, or take a class. I thought about getting a personal trainer. But then my thoughts quickly turned into getting a personal trainer so that I can lose weight so that I will be appealing to someone else once I find the evidence I need to leave my boyfriend. This is madness! How can I live the rest of my life this way? Never trusting happiness; always waiting for the rug to be pulled out from underneath me. I just don’t want to be this anymore. Then I start wondering is this human nature or is this my good friend BPD kicking in. Will I always second guess my emotions? Do normal mentally healthy people second guess their emotions? Anyway, if you do choose to reply, please don’t tell me the obvious. Such as, leave the boyfriend or just stop thinking about it. Because everyone here knows those words are so much easier said than done.