Yeah it's funny because I never really gave it a second thought as a teenager, it was quite irregular even then, id get it on time one month & then it would be two months before the next one or it may be 2 weeks late etc, but you tend to put it down as just the fact the your young etc. Then I was on the pill for 10 years & it's always regular so again you don't think about it until last year when I got off the pill in the hopes of getting pregnant & every time i've got my period the length between them gets longer & now it's about 4 months between them! You'll be fine, im sure of it & the doctor is obviously very confident of it & they wouldn't say that if he didn't believe it so try & think positive & relax & ill think good thoughts for you too;) By the way do you ever monitor your body basal temperature? I've been doing it but it's doing my head in so I think ill stop as im analysing it too much.