itchy after i have had sex for the first time?

Hi,
Welcome to ehealthforum,
Vaginal itching can be due to infection, dryness, chemical irritation, allergic reaction to seminal fluid protein, etc. Visit your doctor/gynecologist for examination and vaginal swab/smear test (done on the discharge) to identify the causative agent. Get started on treatment as appropriate (based on examination and investigations results) 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. If infective cause is detected, and if you are sexually active, 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.