What Causes A Vaginal Fluid Flow After Intercourse?

Hi, We have been trying for a baby for the past 11 months but I have not been able to conceive till now. I had hypothyroidism & am taking the medicine for the same. My TSH & T4 levels are normal since August 2010. Every time we finish, the fluid flows out of the vagina. I'm not sure if thats interfering. If yes, what do we need to do?