What Causes Tingling In Hands?

Please help Ive been going to doctors since 07 I get these episodes where upon standing usually (sometimes reaching for something stretching etc ) it started with just my vision going but its progressed my hands get tingly I feel my heart pumping hard Ive gotten so weak Ive collapsed I slur after Ive gotten pressure in my head Lately they include shaking and extreme confusion sometimes See all my episodes are inconsistent they'll be different all the time i was thinking maybe pots because my limps turn purple easily (pooling of the blood?)
Please someone give me another opinion Ive seen neurologists cardiologists and many other doctors and had multiple test still nothing its just getting worse
Thanks for your time!