I wake up with nausea around 3 am for the past few days. when i try to change my position it gets worse and my heart goes a little fast. im afraid i have some sort of vascular problems. i been to cardiologists before and my cardiac exam was fine?

I would think about GERD. Your body is talking to you. Listen and take good notes. Such as what did u eat/drink/before bed for example. Recommend you go to uptodate.com and spend a bit to learn all about what might be causing this. Then discuss your Dr. Ask family about similar issues,& gall bladder issues. Very unlikely a heart problem.

Perhaps seeing a gastroenterologist would enable the quickest assessment. If there is a residual need for seeking the opinion of a cardiovascular specialist as well, your GI doctor could make that judgement.