I decided to stop taking the pill after my period last week. I would have started the new pack 5 days ago. Could it be causing sore breasts?

Yep, definitely. I stopped the pill just over 2 months ago and had the following side effects: cramps, backache, sore breasts, and nausea throughout my cycles both months. Just finishing with AF this month so hopefully I will do better. The nausea is so old. Also, your period may be delayed somewhat right off the pill--my first period off the pill came at 5 weeks, 2nd period at 30 days. Some women have regular periods right away but there are others who may go several months before getting a period again, so don't freak out too much if you're late this month.

Actually, any weird side effects you get since you quit the pill are expected and not unusual. Anything weird that you don't usually feel is most likely due to your withdrawal from the pill, so don't freak out. And regardless of what your doctor may say, it is ALL related to the pill. Remember that doctors are getting incentives by the drug companies to keep people on their drugs, and the pill is one of the biggest cash cows out there for the drug companies.

Anyway, I just wanted you to know to expect anything, but fear nothing while you're going through pill withdrawal. I was lucky and got my period 28 days after quitting. Many, many, MANY women have to wait a lot longer for their first period off the pill. It varies. It's a crapshoot. But if you want to try to help it along, try getting some Vitex at a health food store or you can order it online if you don't have a health food store near you.

Thanks for the responses. That would explain the lower back pain and cramps.