Performing qasar salaah while studying safar distance away from home

Q: I am from Peshawar and I am an employee here in Islamabad. I used to come to my office every Monday and go home every Friday. I live here in a hostel for 4 nights every week for the last 1 and half years but I have never stayed for more then 10 days here in my hostel continously. How should I perform my namaaz? Do I have to read qasr or full namaaz?