This is not likely to be UTI, it is most likely an allergic reaction. If you have had any recent unprotected sexual exposure, this could also be an STi like chlamydia, etc. If there is any chance of STI then you should go to your doctor and get tested.
One of the commonest causes of such sensitivity and swelling of the vagina not associated with discharge in younger age group is contact dermatitis. You should assume this to be the cause first. Treatment is to search for the irritant cause, such as soap or underwear, etc. If you find anything new which might have caused this, you should avoid it. You should take Tab. Alavert10 mg once daily for 10 days. You should also use Cortizone 10 steroid ointment twice daily on the area. Both of these are OTC
These two steps will help you to clear this.
If this does not help, you should consult your doctor, preferably a gynaecologist and get checked up. Yeast and BV needs to be ruled out. STI also needs to be ruled out if relevant. You may also need investigations like a PAP smear. Discuss all this with your doctor.
There are many dermatological conditions like eczema, psoriasis, lichen planus, lichen sclerosis, etc which can cause such itching and which need to be seen to by a dermatologist.
Hope I have been able to clarify the situation for you and helped in resolving your query.
If you need more help, please let me know so l can continue to assist you.
Thank you and I wish you the best of health - stay safe!
Dr. P. Jyoti