Tobacco gives some people headaches. Though at 15 blunts a day, I wouldn't narrow it down to the tobacco. If it were me, I'd give smoking in general a break and see what the deal is. Sobriety can be fun as well you know. Then after a few days of being sober hit up the bong exclusively and see how you feel. If things are still cool SLOWLY reintroduce blunts. Thats just me though... good luck with the head.