Hi,
Welcome to the ehealthforum and I am glad to help you out. This burning sensation after urinating can be due to urinary tract infection. Please get your urine analysis done and you might need a urine culture as that helps in deciding the right antibiotic to be used. Also if there is any increase in foul smelling vaginal discharge then get a vaginal swab done to rule out any vaginal infection as well.
Please ensure that you take lots of fluids and also pass urine after the sexual intercourse. You should consult a gynaecologist for the same and get yourself physically examined. I sincerely hope this information helps. Take care.