Welcome freshpearl. No one here can diagnose your boyfriend and I don't think a Psychiatrist would either until he had his addictions under control. Often alcohol/drug use and or withdrawals can cause moodiness.

From your post it sounds like your boyfriend is having a hard time. The drug/alcohol abuse may be the result of an undiagnosed mental illness or he may be trying to self soothe with food/alcohol/drugs. Seeing a therapist would probably be a good place to start.