The burning feeling during intercourse can be either due to trauma or infection.
Allergic reactions can be used ruled out as you have been using the medication since 4 months.
So...it will be better to consult a Gynecologist to find out the exact cause.
Also the application of vaginal lubricants during intercourse will help to reduce the discomfort.
Other than that eat a healthy diet, exercise regularly, avoid stress
, get good sleep, think positive and stay happy.
Wishing you good health.
Thanks & take care.