Why do I have pain and burning while urinating?

It's common for menstrual cycles to vary occasionally in length, and a delay of a few days is not a serious issue always. Norethisterone is usually prescribed to delay periods, but if you've taken the medicine and still haven't got periods then consult your doctor. 

After sex, it usually takes 1-2 weeks to tell if you’re pregnant but sometimes there are signs like nausea, tiredness, or changes in appetite which occur when a fertilized egg attaches itself to the wall of the womb. To make sure though, take a home pregnancy test; it’s easy and will give you an answer.

Sexual activities while menstruating normally minimize the chances of expectant mothers since probable ovulation is ruled out. Furthermore, chances are lowered by withdrawal before ejaculation. In the instance you also take emergency birth control pills such as Unwanted 72, chances are further minimized. All the same, there is still a small risk of getting pregnant. If one does not menstruate as expected or develops unusual symptoms, best to go for a pregnancy test. 

You may have vaginal infection, which manifests in the form of itching and white discharge. It is advisable to see a gynecologist that will identify and manage your condition in an amicable way. Also, it is recommended not to use any aggressive soaps or perfumes at the genital and follow good hygiene rules.

It's possible you have a URINARY TRACT infection and a rash.
UTIs can cause pain in lower abdomen..... Get tested!! and treated.
RASH could be unrelated or a side effect of medication.
Consult with a doctor for proper diagnosis and treatment.

It's not probable for you to be pregnant if your menstrual cycle arrived even if it was a little different than usual. At times, periods may be lighter or heavier due to factors such as stress or dietary changes. Cramps and clots are also normal occurrences during menstruation. However, if you’re still concerned about being pregnant, take a pregnancy test.