What should I do if I have severe symptoms of cystitis?

Hello

I've had severe pain since this afternoon, including pain when urinating and general abdominal pain. I get bladder infections very often and know I have one again based on these symptoms. Heat doesn't help much and it's really unbearable. I'm hoping you might have a few tips to ease the pain. I'm drinking a lot but I definitely plan to see the doctor tomorrow. I also have some antibiotics left over from my last infection. Could I take them? Or would they work again?