Heart rate jumping from 100 to 202 in 2 seconds after walking up stairs

24f with a history of refeeding syndrome and QT prolongation. Multiple cardiac admissions for electrolyte imbalances in 2024. Currently, I just have IST, a mitral valve prolapse, and a history of severe stimulant abuse. I took phentermine 37.5 mg this morning. Yes, I know it’s dumb. And yes, I’m considering going to rehab. My heart rate hitting 202 isn’t crazy for me, but it’s the fact that it jumped so quickly that concerns me. Is this something I should go to the ER for? Tachycardia isn’t abnormal for me and I’ve never had complications from a high heart rate. But I do feel kind of out of it when I stand up. I also started dry heaving which always happens when I hit my max HR. My HR quickly went back down to 100-110 within 20-30 seconds.