I have only ever had sex with 5 people in my life, and it was always when I was in committed a relationship with each of them.
(I understand that each partner may have a past.)
This is a great question because the trouble with trying to analyze our own symptoms is that often sexually transmitted infections and other kinds of infections have similar symptoms.
In order to be diagnosed you’ll have to describe your symptoms to a health care provider. They’ll have some follow up questions that may be able to get to the root of the issue, like where and when exactly it hurts. From their assessment they can advise you as to what tests may get a diagnosis. They can screen you for STIs and/or bladder infection. The good news is that there are treatments for both.
It’s recommended that anyone who is sexually active build routine STI testing into their health appointments. The national guidelines for STI testing encourages that “serially monogamous individuals who have one partner at present but who have had a series of one-partner relationships over time” be tested routinely too. Talk with your doctor about how often is right for you.