watery pinkish discharge

I am a 30 years old lady. I had a child in the year 2001 and have continued dating the father of my child. I recently had an affair with someone else. The last two times I've had sex with this new guy left me with a pinkish watery discharge. I thought it was an injury in me, but just had sex with the father of my daughter a few days after and found there was no such thing at cleanup. Could it be from the semen or does my system react to the second guy. Please note I have had myomectomy about 18 months after I had My child.