Hi, I'd like to help you with your question.
It sounds like there are many issues here. One is your boyfriend's behavior from before the war and whether or not he may have had mental health issues then. Also, there is the questions of whether or not he is having trouble because of the war, possible Post Traumatic Stress or another issue. Then there is the relationship between the two of you.
The main concern in this whole situation is that you are allowing yourself to be exposed to your ex boyfriend's behavior problems, potentially making you a target if he chooses to act out towards you or loses his ability to control his behavior. You need to decide if you are willing to continue to allow yourself to be in this relationship and expose yourself to possible danger, or you can set boundaries and stop seeing him.
I highly recommend you seek out counseling to help you deal with this relationship and find answers you seek. A counselor is bound by ethics to keep anything you tell them confidential unless there is a direct threat of harm or there is child abuse involved. You can let the counselor know about the situation and they can help you find ways to deal with it.
Also, encourage your ex to see a counselor as well. It sounds like he has been to see someone if he is on medication, but if he can get into regular counseling with talk therapy, that is better. With a counselor, he could gain a better understanding of what his diagnosis is and receive the proper treatment. There are many more advances these days with treatment with so many veterans coming back from the war with Post Traumatic Stress Disorder and other mental health issues.
Whatever you decide, it is important that you keep yourself safe and do what you need to do to take care of yourself.
I hope this has helped you,