This is caused by inflammation of the bladder (cystitis), which is contracted during sex. In the case of cystitis, bacteria enter the bladder via the urethra and irritate the mucous membrane. It then burns like hell when you urinate and you feel the need to urinate frequently. It often helps to drink two liters a day, including bladder and kidney tea, to flush out the germs.
Severe pain
If there is also nocturnal urination and severe pain, it may be a case of interstitial cystistis (IC), an inflammation of the bladder wall that mainly affects women. It is not caused by bacteria, but the exact cause is not yet known. The problem is that it does not go away, not even with antibiotics. A cystoscopy shows whether someone is suffering from IC.
Infection
Urination is also extremely painful in the case of vaginitis. However, it "burns" mainly in the vagina.
Irritable bladder
This is typically characterized by an excruciating urge to urinate or involuntary urination; burning pain, as in the case of inflammation, is not common. However, some patients complain of a painful, constant irritation. Behavioral therapy and pelvic floor exercises can often help here.