I would give up for a bit. You have the rest of your life to get blazed and it is a load easier to do alright in exams the first time than resit them. If I have weed I will smoke every day and have no will power to not do it. If I don't have weed I can cope easily with out it. Just run out or sell your weed then don't get more untill after your exams. The sleepless nights and feeling shit will only last up to 4 days, well at least for me.