Hi! I'm 45 now, but a few years ago I was running into the same problem as yourself. I was having alot of discharge during the day where I had to resort to wearing a pad. i went to my gyno back then and I had a BV infection. He said it was not caused by sex, just an imbalance in the vagina. I was treated for this imbalance for quite a few months. It would always tend to happen right after ovulation which would tend to throw my levels out of whack. Just last year my gyn said I'm in peri-menopause, periods running every 20 days, spotting, mood swings you name it. Maybe back then was the start of my peri-menopause and maybe this is what's happening to you. To ease your mind, I would go get checked, they will take a culture and can usually tell at the time if things are off. It just may be coincidence that your having sex now, but we are at that age where our bodies are starting to change. I wouldn't be worried, just get checked out and you'll feel better.
I'm not sure what you are asking but 1/2 cup of discharge a day does sound like an awful lot.