What Causes Abnormal Period Along With Sore Breasts?

I am a stage 3 papillary carcinoma survivor, and i am finally on the correct dose of synthroid. And my husband and I have been wanting a child, but I was not ovulating for a long time with my body being out of whack. I have taken ovulation tests for a LONG time time and never got a positive result until a few weeks ago, while my husband was home, and we had sex a day before my test said I was at my peak. I should also note my periods have been on time like clockwork for the past several months since my synthroid was adjusted to the right dose for quite some time. I should not have my period until Sunday, and today is Thursday, but I started bleeding slightly this morning. The bleeding has gone on all day, and is a pinkish red color, but is very watery. I have been very tired and moody, which is usual for PMS for me, but my breasts hurt VERY badly. I have had periods since I was 11, and I am now 29, and they have never been watery. I get paps done every 6 months and they are all regular and my husband and I are both faithful to each other. So my question is...what is going on?