Low Blood Pressure. High Pulse

I am 23 years old and weigh 105, 5'3 and I have very low blood pressure and high pulse. My pulse is usually over 100 and pressure 80/50 and gets as low as 60/40.  I get bad dizzy spells and black outs. I changed my diet, water intake, no caffeine, and have normal exercise. When it happens I feel a flutter in my chest and and very dizzy. I also get nauseous and turn completely pale.  This happens anywhere, anytime, not just from standing up/ sitting down. I am also very tired lately. What could this be?  

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You really need to be seen by a cardiologist for this to find out what is going on. :)