My FP has set boundaries for our relationship and it became perfectly healthy now, but I just can't help but splitting. The lack of constant reassurance makes me feel like I'm settling for less and I'm not special to her the way I was.
I'm aware when a splitting episode kicks in and I do deep breaths technique to avoid it, but it just keeps appearing so often that it doesn't feel like splitting sometimes and it's how I really should feel about the situation. 
Every interaction she has with another human being than me feels like a threat to me and there is no reassurance to be sure that it's not.

How can I not be so possessive about her?