So I have BPD and PTSD, I've always struggled in relationships but I've finally got a good one. My boyfriend is amazing and supportive, his mum has really, really severe mental health issues that make me look well in comparison so that's helped with him understanding me. My problem is that whilst I feel like he's my soul mate most of the day, every single day I have doubts. When I think of him leaving me I literally can't bare it. We've spent every single day together for three years now, but these doubts are playing on my mind. They scare me, I wonder if I should be with him if I keep doubting so much, then I wonder if it's just my condition causing these feelings. I just want to know if this is normal basically. I want to marry him, I want to be with him for the rest of my life, is it just my mental health that's making me doubt things? Relationship advice tells me I should walk with how much I doubt this relationship, and that terrifies me. But then I wonder if normal relationship advice even applies for me. I just feel so lost. I've managed to overcome substance abuse, food addiction and all forms of infidelity for him, I've lost 21 pounds (I also have a binge eating disorder) so far all for him. I do everything for him so why do I still doubt this relationship? 

TL:DR In great relationship, but keep having doubts, is that normal for people with bpd? 