Yellow-Greenish Discharge After Sex With My Husband?

My husband and I were both tested for STD's before we were married and are both clean, no cheating on either end. In my entire sexual history I have never had this problem, but every single time I have sex with my husband I get a yellow-green-clear ish discharge for the entire next day. Other than that time, the discharge is absent, no pain, no itching, no nothing. We have been sexually active together for three years now, and right before we married we both had a fling with another partner. (hence why we tested before the wedding.) Still, with that one other person, I had no discharge. It has only ever been with the man I am married to, and it has been every single time we have ever had intercourse. The other woman he has had relations with never had this problem. What could it be? Could I possibly have some type of allergy to his semen specifically? Also, there is a vaginal odor that comes after sex also during the day after. Other than this, I never have this type of odor. I have read that the odor could be due to a PH differential between the partners. Could this also be the cause of the discharge? Also too, we have been trying to conceive for 15 months now with no success. Any ideas? Please help!