As described, the skin lesions don't sound like any STD. Genital warts (due to some types of HPV) occur rarely on the buttocks and never, to my knowledge, on the upper body. You'll need to see a health care provider for a diagnosis.
Vaginal discharge is an other thing, and abdominal pain is worrisome. There are too many possible causes to speculate, and you don't say anything about your sexual lifestyle (new partner, multiple partners, partners' risks, etc), so I can't speculate about STD as a cause. But get it checked out.
Good luck-- HHH, MD
ALSO REMEMBER THAT HPV COULD INFECT THE CERVIX(CAUSING CERVICAL CANCER IF NOT TREATED)U MIGHT WANT TO TAKE A PAP SMEAR RIGHT AWAY (AS WELL AS STDS FOR CLAMYDIA (chlamydia) AND GONORRHEA) TO SEE IF HPV HAS AFFECTED YOUR CERVIX(ABDONIMAL PAIN AND LOWER BACK PAIN ARE ASSOCIATED WITH IT)REMEMBER THAT U COULDVE HAD HPV FOR YEARS AND NOT HAVE SYMPTOMS. ALSO KEEP IN MIND THAT STDS DONT CAUSE SYMPTOMS RIGHT AWAY,IT TAKES A PERIOD OF TIMES FOR THEM TO SHOW UP.(AGAIN IM NOT A DOCTOR I JUST TRY TO HELP PEOPLE,IVE BEEN THERE TOO)GOOD LUCK