Why do I suffer from chronic acid reflux issues despite eating a healthy diet?

Hi,

I am a 17-year-old female who has been suffering from bad acid reflux for the past three months. It is bad enough that I sometimes get vomit in my mouth when I bend over, and this does not happen after a meal.

I have a healthy weight and eat a well-balanced diet. I tried Zantac 300 mg, but it did not work; now, I am taking Nexium 20 mg, which helps with the acid, but I still have reflux.

I take some regular medications like Esomeprazole 20 mg once daily for acid reflux, Topiramiate 25 mg twice daily for epilepsy, Seretide two puffs twice daily for asthma, Escitalopram 20 mg once daily for anxiety, Eletriptan 40 mg for migraine, but my doctor has checked and told me that these medications do not cause acid reflux. I had a gallbladder scan, and it came fine. Please tell me the cause and the treatment.