Hi,
Thanks for the query.
If you had
unprotected intercourse around the time of ovulation there is possibility of pregnancy.
Irregularity in menstrual flow can occur due to many causes.
Hormonal imbalance can cause
irregular periods, intermenstrual spotting etc.
If the is pregnancy the spotting could be due to
implantation bleeding or
miscarriage or due to some other causes.
For more details : http://srsree.blogspot.in/2013/06/causes-of-bleeding-per-vaginum-other.html
Prolactin hormonal abnormalities can lead to menstrual irregularity and
breast pain, secretion etc problems.
So, consult gynecologist once, get examined.
And go for ultrasound and prolactin levels estimation.
This will help in ruling out the possibility of pregnancy and to detect the cause for your problem.
Then treatment can be taken accordingly.
Take care.