New to reflux

I’m a healthy 37 year old. Not under any stress and never had reflux before. I’m trying to piece together why I’m suddenly overnight suffering from GERD (been 3 weeks now). Had a 2 week holiday the weeks before and did get stomach flu which I did take some time to recover from. Took something for it too. I then also had a dentist appointment where because of worn enamel on one tooth, I had some sealant put on. The symptoms started that day, with my throat feeling irritated more near my tonsils (it felt like something was stuck there), then over the next few days it felt like something was stuck in my throat, which grew to feeling tight at my lower throat/ in my chest. The irritation subsided a little but the latter feelings now haven’t gone away. Instead I’ve had headaches, feeling I want/ need to burp, burning in throat and feeling food is stuck in throat. The last few weeks it has got worse and I’m so uncomfortable. I went to the dr after 7 days and they gave me 20mg nexium and suggested I come back a week later if it was still bad. I did and she is sending me for blood tests and an ultrasound, convinced it isn’t acid reflux as the nexium didn’t work. That maybe it is thyroid. Still waiting for these tests. In the meantime I naively hoped if I kept my diet sensible (been reading up on do/ don’t and I can’t make big changes as I’m already healthy) that it would disappear. I’m still uncomfortable and it’s creating a lot of stress now (which I know doesn’t help!). Any reassurance, help, guidance welcomed!