What you describe is POTS. Don't waste your time for the diagnosis as they think it is caused by an unknown bacterial or viral infection
I had what you describe very early on in my treatment. I went to about
10 cardiologists before I was sent for a tilt table test and was told it was POTS.
There is no real treatment for it. Beta Blockers and increasing your salt intake are recommended. I have done both with no success. My old LLMD says many with Lyme get POTS and it is very common and just part of the disease.