same kinda thing happened to me but not as dramatic. I had been smoking for 5 years maybe, 4/5 yrs. nearly every day. then when i was 16/17 i started 6th form (uk just b4 uni shit) and my life was shit, i didnt kno what i was doin where i wanted to be in life etc etc, hardly went out just sat and smoked. and i knew the weed was to blame. I gave up half way thru 6th form, worked hard, got decent grades now im off to uni soon and only smoke every other day taking 5-6 day breaks now and then (mainly because im skint!).

anyway the point myself and others have already made is definatly try giving up weed for a while at least.