Thanks for the replies. I guess i'm in the wrong place on the the forum then - I just did some research on BPD and it does actually fit many of the symptoms. I don't see him that often so i'm not sure I can say if he has substance abuse issues, but he does drink heavily.
I have never talked to him openly about this, since he doesn't really admit it or wouldn't say there's something wrong with him.

I just figured something must be off if he can show such extreme emotions towards me and wanted to spend time with me, express his feelings for me, and then just several days later ignore me like it never happened. It's hard to believe that his actions were only fake or perhaps it's easier to push the ones you love away?

I guess taking a step back is the only thing I can do. It's just so hard to love someone so much and seeing them in pain or not knowing what's wrong/how to help. I wonder where the man I love went.