I cannot understand why your doctor is not helping you. If the doctor that you went to is not helping, make an appointment to see a different doctor at the practise. The doctor should examine you and take a swab to send to the laboratory to check if you have a bacterial or fungal infection.
Sometimes having rampant sex can also cause bacteria to up the short urethral tube and into the bladder causing Cystitis which is a urinary (pee) infection. And really the doctor should take a urine sample to check.
It would be a good idea for your boyfriend to go to his doctor or the GUM clinic to get a swab taken from his penis to make sure that he does not have any fungal or bacterial infections that he is passing on to you. Make sure that he washes his hands before he touches you, as hands do carry bacteria.
The most highly chance is that you have a fungal infection. You can buy from the pharmacy an antifungal cream and a pessary to insert into your vagina. If you are too embarrassed to get this yourself, ask your boyfriend to ask the pharmacist for his advice to purchase the antifungal medication for you and then follow the instructions on the packet.
If you are experiencing pain when you pee, you will need a different medication for this as it would indicate that you may have a urinary infection.
Just to remind you, even though I do not know the age limit to have sex in your country, that it may be illegal for you to have sex and illegal for an 18 year old to be having sex with you.
No doubt you will have sex, regardless, but do make sure that you always, and I stress, always get the bloke to use a condom. If he doesn't have one, then don't have any sex. Don't let any bloke use you.
At home for immediate relieve, wash yourself with water only and apply natural set yogurt to your vagina. You can buy natural set yogurt from most grocery stores - just make sure that it is the unsweetened one. You can apply this for as long as you need to, but if the symptoms do not settle in a couple of days, you will require medication.
Best wishes.
Have your bf tested for STD's or an infection...see another doctor.
A perfect guidance to follow by the sufferer.