Medical leave, with PTSD and being investigated?

I'm a AGR in Cal, my Doc just put me off work for 3 Month. The BN is not happy about this. The Doc's telling me I have PTSD and 3 other conditions. They are going to investigate the PTSD, I was not in combat, so they don't understand how I could get this.. Im over worked and Strees out. No sleep and so on. Could use some help with this issue about the Leave. I have been reading 600-8-10 but confusing me more.