Two/three weeks ago i was having abnormal heavy yellow vaginal discharge and some itching there. my doctor said i might have trich, so i started taking flagyl twice daily for seven days but it didn't work. i'm still experiencing same things?

Infection? STD?: There are many causes of abnormal vaginal discharge. "Heavy yellow" strongly suggests an infection, especially an STD. If your doctor suspected the STD trichomonas, presumably you were also tested for gonorrhea and chlamydia, right? If not, get tested for them ASAP. Yeast is possible, but usually just itches, without much discharge. Return to doctor for further evaluation; no sex in the meantime

Trichimoniasis: Agree with Dr. Handsfield. Since you indicate the doctor said you "might" have Trichimoniasis, that suggests that you were not actually tested for sexually transmitted diseases. If that is the case, please seek reassessment with STD testing.