I'm so sorry this has been happening.
What kind of doctor did you see? What is the name of the medication that he gave you?
Is there a walk in clinic near you - like an urgent care or STI clinic you can go to? What about an emergency room?
It does sound like it could be an STI, but I can't say that for sure. It could be a really bad yeast infection or bacterial vaginosis, too. Without testing, it's impossible to know.
When you go, insist on testing, and insist on being examined. If they think it's herpes, ask them to do a PCR swab on it. Since it's been so many days, the PCR swab is better than a regular culture because it's far more sensitive.
Make sure they do a type specific swab, too, because if the guy gave you oral sex, it could be genital herpes type 1.
Don't panic, though, really.
In the meantime, if it hurts to pee, pour water over yourself when you urinate, or get a latex glove and cover the skin with your hand when you pee. Make sure to drink lots of water, too, because the acid in your urine is what hurts when it hits the sore skin, and the water will help dilute that.
Whatever it is, we will help you through it, and you will be okay.