I don't really have a lot of discharge. However in certain light it looks yellow. It is all dry and it is just several small spots on my undies.

May possibly be bacterial vaginosis wich is common in women who are sexually active or have had there first few menstral cycles it is mainly an out burst of bacteria growth in the abdomen wich have grown in excess baths in unclean water or with certain soaps may trigger such things,. it is best if sexually active to urinate before and after intercourse emptiing out your bladder completely wich will also help avoid other common problemns such as kidney and bladder infections,. and remember no sex is worth having if it isn't done safely with the proper protection and practices...

There's no way anyone can guess. Candypascual suggested bacterial vaginosis, which is a possibility, one of hundreds, but without seeing a doctor, there's really no way to know for sure.

We can't and won't diagnose you on this site. It's not only impossible, but it's against the rules of this site. Not even a doctor can give you a diagnosis over the internet.

So please see your doctor. This could be something mild, or something very serious if left untreated. You don't want to take a risk by accepting a diagnosis that isn't a sure thing, on the internet.