I was on a low estrogen pill for about 6 months to a year (i don't remember exactly how long).. The first couple of months I was perfectly regular but then my periods started getting out of whack as well... I was late one month... Then I would get spotting and almost have 2 periods in a month.. Then it would change again. For me it was the low estrogen .. It couldn't maintain a regularity for me.. I would give it some time and if it doesn't come then go to the doctor.. They may have to change around your pill.. If you were good about taking it every day then I would highly doubt you're pregnant.

I have been on ortho trycyclen lo for 2 months now and I am not happy with it. I think for me it is the low estragen too. I had been on the ortho tryclyclen for 2 years and it worked great for me.. Cleared my acne, and regular periods were no question.. So now I am going back on ortho tryclyclen again becasue I had better luck with it..

Write soon!!

I was on ortho tri lo as well, and I went off of it after two months....It made me break out, which had never happened in my 19 years, it made me tired, and the side affects were just not worth the security of the pill.

I've been on ortho-lo since june and it works great for me. Periods are always on time and a pretty light flow, which is amazing. Anyway... Everyone's body reacts differently to stuff, and even though it might have been fine for a while your body is still adjusting to it.
Also, if you havent had unprotected sex and forgot to take your pills or something like that you should be a-ok.