Can anxiety cause rapid heart rate when standing, over 100 bpm, and muscle weakness? I've been experiencing this for a month. Docs can't find anything

Yes. Yes, anxiety can cause these symptoms. I'd recommend treating your anxiety as aggressively as possible with medication and psychotherapy, and then seeing if these symptoms decrease. I see that you're taking birth control pills. Sometimes birth control pills can contribute to anxiety as well. You may want to discuss this possibility with your physician.