Struggling with Negative Thoughts and Guilt in My Relationship

My boyfriend is wonderful and treats me as close to perfect as you can get. But my ptsd and bpd fill my brain with so many negative thoughts and fear of abandonment that I feel like I’m ruining him. I try so hard so work through those thoughts and feeling but sometimes I let them go and spiral into an episode. Afterwards we talk and he assures me he understands but I fill with so much guilt that I think about leaving in regards to the sake of saving him from myself. The only advice I receive from those around me is “well if you can’t trust him leave” but it’s nothing he does it’s simply my mind. Just needed and outlet thanks if you read any thoughts advice or support is greatly appreciated.