Hi. I Had Sex While My Girl Was On Periods.

hi.
i had sex while my girl was on periods. i am facing pain and burning internally in the tip of my penis. i am facing this problem since the second day of the sex. i am very very worried about it. i think i got some type of STD(Sexually transmitted dieseas). what test should i have done to to know that why type of STD it is. i often feel pain i both legs too. and irritatation in urination everytime.
i shall be very very thankful for the help.