Help please!!

Just found out my fiancé is on meth! I knew something was going on but tried to forget about it. He got to the point of accusing me of cheating and plotting against him. Sweats, scratches and mumbles to himself.  I just found in our garage pipes n bags! He says its meth. Idk what to do or think. I'm scared. My stepdad was on that shit n he ended up kidnapping a family and stabbing his self. Said the devil told him to do it. I am worried about my unborn child. Please help!