Bipolar Ex going back to old ways

I was with someone for two years who had bipolar but was diagnosed about a year ago. Our relationship was a complete rollercoaster. Lots of breakup and getting back together, lots of heartache, and he did lots of drugs. Had bad PTSD from the military as well. Once I left him he went back to rehab and finally got clean and has been for 2 years. We became friends again last year and made amends. He got off his bipolar medication half a year ago and he is slowly pulling away from me, slowly becoming cold, and slowly becoming more miserable. He texted me last night after a month to see how I was but he barely made conversation. He just says a couple words then disapears. keep asking him whats wrong and hes just cold and mean. This is really troubling me and hurting me (once again) and Him being a jerk is just killing me. I'm not really sure how to deal with this. I have to learn that I can't save him and we are not together anymore so it's not my job to help him. What should I do? the more I try talking to him the more he pushes me away. Is this normal?

If he is off his meds then probably anything he does is normal. Unless you can get him back on his meds maybe you should be just friends and nothing more than that. It probably won't end well for you if you try for more. Learn all you can about his illness and maybe you will figure out something that will help him, be supportive as a friend and stop there.