I broke up with her over 7 years ago because of extreme emotions due to BPD. But I still try to contact her every few months and think about her all the time. It seems like an addiction.

The thing is, I really want nothing to do with her. I have a good career and the perfect girlfriend now and I know that even if my ex replied to me and begged me to get back together, I wouldn't have a single urge  to reciprocate. I have zero attraction to her now and I think my current girlfriend is a million times better in everything than my ex. 

At first I thought it was just my ego being hurt that she isn't replying to me and I want to gain back control over the situation. Maybe it is what's happening and I'm in denial. But to me it feels like a completely irrational obsession fuelled by emotions (used to have that with other people before my ex). Thoughts of nostalgia pop into my head and I fantasise about her without any control over myself. Sometimes I even actively go to places we used to hang out together in the past just to reminisce. 

It's completely fucked up and seems to be out of my control. Even when weeks and months go by without thinking much of her, feelings and thoughts can suddenly come flooding back in once I'm reminded of her. It happens more during times of emotional stress, but not exclusively.