Severe backpain,stomach pain,vomited 1 at night,burn when peeing,after pee feels like need to go again,sex 5 times(protected),period due 1 week,16 old?

Bladder infection : You likely have a urinary tract or bladder infection. Women are prone to urinary tract infections because the tube that goes bladder (urethra) is short. Frequent sex can push bacteria up into the urethra and onto the bladder. See a doctor and start treatment to prevent the infection from spreading to your kidneys. Urinate immediately after sex and drink lots of water to prevent a recurrence.