is it an STD?! I've had a yeast infection twice...

Hi,
Welcome to ehealthforum.
The labial/vulval itching that you describe could be due to infections, pH imbalances, opportunistic infections, hormonal insufficiency, chemical irritation, etc. Look out for development of any new symptoms like alterations in vaginal discharge consistency, appearance, presence of foul smell, etc. You should consider visiting your doctor/gynecologist for examination and to go ahead with getting hormonal analysis (done to rule out dryness or itching caused by hormonal insufficiency), vaginal swab/smear test done (to confirm/rule out infective causes), etc. If the itching is getting worse, you can also request for prescription of antihistamines to help you control the symptoms. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet and lifestyle. Avoid vaginal douching, use of harsh soap or perfumes in the area. Use loose cotton undergarments and avoid use of tight fitting clothes. Avoid sweat accumulation in the area and keep the area clean and dry. Rinse undergarments well and use antiseptic solution for the last rinse. If infective cause is detected, it is important to get your partner also treated simultaneously to prevent chances of re-infection, and avoid having intercourse while being on treatment.
Take care.