It depends on how yellow it is--faintly yellow and normal smelling is fine, but thick and truly yellow and foul smelling is not so fine and could be signs of an STD. If by "virgin" you mean no oral, vaginal, or anal sex or rubbing of genitals with someone else ever, though, then an STD is exceedingly unlikely.
You should maybe get those cysts and prolactin levels checked out again, and ask the doctor about the discharge while you're there.
thanks for your concern and kind comment. however, I've heard that a yellow discharge is not a good sign. Thanks anyway
Well, yellow-ish discharge is normal, as long as it doesn't smell foul or fishy (which if I'm reading your post right, it does not at this time). Some women have a lot of discharge, and I don't know of anything that can be done about it. Sometimes I have enough to make my panties quite wet, and it's pretty annoying. You could use pantiliners to catch the wet, and just change those out rather than having to change your panties.
Using less sugar, eating more yogurt, and wearing cotton panties are all for trying to prevent yeast infections (don't know how well the less sugar and yogurt ones work, but they certainly won't hurt anything). You should ask your doctor if you're putting a vinegar solution inside your vagina. That could potentially mess things up, since generally speaking, the vagina is a self cleaning organ best left to its own devices.
I guess hormonal changes could be what caused the extra discharge, but I really don't know enough about it to tell if that could actually be a factor or not.
As long as you're keeping whatever you use to masturbate clean (fingers/toys), I don't think it would have any effect on your discharge.