Hi--I'd like to try and help you. Where were you deployed in the service? Besides viruses, there are chronic bacteria and parasites found in many countries, often contaminating the water. Also, does any chronic bowel disease run in your family?
Something debilitating like this shouldn't take weeks to get evaluated by the doctors.
I am on the West Coast of the US, about 8 hours from GB, so if you answer there may be a delay in my response but I will respond. I have seen people have amoebic dysentery for a year and more and don't want this to happen to you. The problem can be infection or autoimmune but it needs be sorted out.
You need to put in a sample of the worst, most liquid diarrhea several times for a check of "Ova and parasites"
Those countries are rife with parasites.
Odds are picked up in Nepal or India as in Afghanistan you probably only at rations.
A treatment if something is found should set you right