See your doctor

I fully agree with the other opinions given.  You need to see your docor immediately for this.  Your prognosis does also depend somewhat on the character of the drainage (e.g is it clear?  red?  foul-smelling? purulent?)   Also - is the outer skin red at all?  Signs such as these may indicate an infection or the presence of tissue that is not healthy inside of your breast (fat necrosis).  Most likely, however, you have a fluid collection (seroma) which should be drained and followed closely afterwards.  If your doctor is unwilling to see you or deal with this problem, then find another board certified plastic surgeon in your area who should be readily qualified to handle the situation appropriately and, just as important, provide the proper follow-up.