Welcome to HCM.
As you have burning sensation in urine,you may be suffering from UTI (Urinary Tract Infection
),which is common following sexual intercourse in female.
Also you have negative result for herpes and STDs. So don't be much worried.
You follow these steps:
1) Clean your perineum
area very well with maintain proper hygiene.
2) Drink plenty of water or other fluid.
3) May take urine alkaliser like Syp URILISER 1 tsf mixed with water thrice daily.
4) May take tab Norflox
400 or Ofloxacin
or other higher antibiotics twice daily for 7 days.
5) Practice safe sex in future.
For more information,mail me.......firstname.lastname@example.org