The most common cause of new, foul smelling vaginal discharge is bacterial vaginosis. That's probably what poco102361 had, although it's a lot more complex than the pH being off. (High/alkaline pH is the result of BV, not the cause.) There are other possiblities as well, including trichomoniasis (which is an STD), other bacterial infections, and more. Some of these can be serious, and all, including BV, require treatment with prescription antibioitics. You need to see a health care provider for proper diagnosis and treatment; don't try to figure this out online or by self diagnosis.
Good luck-- HHH, MD
Hi, I'm no expert but I am a woman and have had vaginal infections. I had one that did have a foul smell and alot of discharge, more then usual and I was diagnosed with a bacterial infection. Dr. said it had nothing to do with sex, just that the ph in the vagina was off. I was put on a cream for about a week to 10 days and it cleared up. I wouldn't wait too long to go see your obgyn. better taken care of sooner then later.
I'm with Poco on this one. Seeing a doctor soon would be a good idea on behalf of your nethers.