I'm only still with my partner because I don't want to deal with the aftermath of us breaking up
Why do you feel you can't break up?
It will cause too much stress, I don't want to listen to his griping
Listening to others gripe and complain is hard to bear, but you need to avoid that by telling him to leave you alone. Get a restraining order if you must. Think positive, many people deal with the same thing and they feel better despite the griping.
I am going to call my ex tomorrow for help.
If you really want to break up it is bad to stay in a bad relationship. You need to take steps to leave, if you feel trapped you can ask other like friends and family for help.