Fainting episodes and resting heart rate is 110 - ECG otherwise normal

It seems to get so much worse in heat, I can’t take it. My heart can go right up to 130 within 2 minutes of standing. It’s worse when I stand but I had an ECG the other day that was tachycardia resting heart rate 110. She said it was otherwise normal though but I just keep getting these fainting episodes every time it feels warm, and every time my heart is speeding.