Weird feeling in my chest

Well I'm 20 and I've been having nausea episodes for 2-3 months now along with chest pain.  I went to the ER and they diagnosed me with acid reflux or anxiety so they gave me zantac and lorazepam.  Well I still have the nausea on and off; however, today I had a new symptom.  All day I've been getting a sinking feeling in my chest down into my stomach.  During this it feels like my heart starts racing and at the end my heart makes a huge THUMP that I can actually feel thru my chest.  It doesnt last too long but its been happening all day every 1-2 minutes and its getting annoying.  It happens when I'm sitting, standing, laying down, anything.
I thought maybe it was anxiety but I used to be REALLY stressed at the beginning of the school year last year but I made some choices to take my time with school and since been much less stressed so I cant really see it being anxiety but I dont know.  I dont know what to do.

Thank you!

[cindy707]

If it were my body the first thing that i would do is to re contact the doc that diagnosed the reflux/anxiety and tell them about this new symptom.  Its only a phone call, the docs are there 24/7 and it will ultimately be up to them to determine if it is heart related or not but they can't know that something is wrong and a new symptom has popped up unless you tell them.  Its always better to be safe then sorry i think.  Acid reflux does mimic heart issues alot because of the corrolation between the organs and how they are connected but the thump could be something else altogether...i'd make the call.