I sounds like an old fashioned UTI.
STOP taking antibiotics! The next time you get a UTI, use D - Mannose Powder.
The lovely petals of your inner lips have nothing to do with getting UTI's.
SUGAR is the problem in most all cases in terms of yeast overgrowth and weight.
It's always a good idea to urinate after partner sex.
Our vaginas naturally have mucous inside that changes with our menstrual periods and diet.
My first line of attack is always diet.
Also if the dildo was made with phthalates, most of us will experience irritation as a result of this toxic material in a product.
I seriously doubt this is caused by masturbation unless you are doing penetration with a dildo that is not a quality silicon rubber.
As long as his "rash" is not painful and your vagina is not causing you any major discomfort, I wouldn't worry.