ABNORMAL VAGINAL DISCHARGE AND SHOOTING PAINS

hi. im 18 years old. after the last day of my menstruation, I had a very odd vaginal discharge. It was yellowish or greenish and is thick, and when it comes out, I experience a burning sensation and itching.  And what bothered me is that I saw a red tinge on it. I think it is blood, but it is only thread-sized. My discharge doesn't have any foul odor.  Another thing that bothered me is I experienced shooting pains in my vagina w/c only lasted for 5 seconds I think. But it was a sharp pain and I  can rate it as 9 (1 being the lowest and 10 being the highest.) I went to our school doctor and she prescribed me with ofloxacin. Maybe they suspect it as UTI co'z I drink only 3 glasses of water a day and i have a dark yellow urine.

Please I am very anxious of my condition. I dont know what might be the cause of my red-tinged vaginal discharge and the burning and itchy sensation. I dont have any sexual partners so I dont think I have any STD's.

Anyway, Im gonna start taking my madication tommorow. The doctor asked me to return after 6 days and  have my urinalysis. I hope it is only UTI. Not any sever gynecologic problems.

Oh yeah, before I forgot, I have also been experiencing left chronic pelvic pain for 3 years now. My ultra sounds are normal, but I am not convinced that I am alright.

Please reply.