I've had unprotected sex just about a week ago and I noticed that I had white vaginal discharge but it started to become more yellowish as the days we?

Vaginal discharge. The color of most "yeast" (fungal) infections produce a white discharge. Most other vaginitis may have degrees of color variation. To be certain, see your gyn provider for an exam and culture of the discharge.
See below. Agree with Dr. Berryman. As you see your doctor, discuss about getting tested for other sexually transmitted diseases as well.
Wish you good health! - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form.
Practice safe sex, if you have sex.