Given the fact that you have irregular periods (last one started on 16 may 2009), it might be difficult to calculate the expected day of ovulation. Ovulation occurs exactly fourteen days before the start of the next period.


If the periods are regular, then the start of the next period can be easily calculated, as well as the ovulation day. However, in women with irregular periods this calculation is difficult because you cannot predict the start of the next period.


As for the pregnancy signs you mentioned (sensitive breasts, some weight gain, and period like lower back pain), they are not specific enough for pregnancy to be confirmed for sure. Home pregnancy tests might be used, but might give false positive or false negative results.


You might want to visit your gynecologist for a physical examination, laboratory hormonal tests, and an ultrasound scan. If pregnancy is not confirmed, then you might want to have regular ultrasound scans several days after the start of your next period. Even if your periods become extremely irregular, your gynecologist might be able to approximately determine the date of ovulation based on the size of the follicle that contains the egg and releases it when ovulation occurs. The gynecologist might also help you to find the actual reason for the irregular periods. The hormonal laboratory tests might identify it, as a hormonal imbalance is a common cause for irregular periods.