Unable to reduce tummy. Please help.

My name offs Shyam. I am 6 feet and weigh around 108kg. This weight is consistent since 2007 (when i had my ACL reconstruction surgery) since then i have done a lot of gym and went to swim as well but unable to reduce weight. My body is in shape but i have a large tyre. Off late my waist size had come down from 44 to 40, but i can't wear regular size shirts because of the tummy. I need to reduce weight as well, but donot know how. I tried some diet plans as well but nothing is working. My lifestyle is more of a work at a desk. 4 hours of travel and 9 hours at desk all the while sitting. I have developed severe back pain as well as acute headache (migraine ish) which is hampering my day to day work. I have a reduced immunity as well and also diagnosed for type 2 diabetes. I am a vegeterian (lacto ovo), but my family members are pure vegeterian. With all these i have developed a lot of stress (financial and personal life included) and lack of sleep. please help.