Keri
I am no expert on what is normal for an 18yr old, but I came off the pill myself in 1997, having many years before, been put on the pill for similar reasons. It took some 18 months for my periods to become "normal" again and I only had 2 periods in the 1st 12 months. I was concerned about this at the time and my GP, very reassuringly, told me that it was perfectly normal to not have, or only have infrequent, periods for up to 2yrs after stopping the pill. I am happy to say I am now as regular as clockwork! Hope this helps...