Argh I wrote out a lengthy detailed reply and then my computer decided to reboot
The abbreviated version: you say your BP is typically low> how low do you mean? low end of normal range or are you talking hypotension? Are you also bradycardic?
I know its easy to assume anxiety as the cause, and it likely is at play but thats a long time to be anxious, especially if you slept a bit and woke up still having palpatations/tachycardia (psst- did you ever take your pulse to check how fast your heart is actually going?)
The reason I want to check this out is because there is a far greater risk of developing an arhythmia when someone goes from being bradycardic and/or hypotensive, to suddenly a prolonged state of tachycardia/ hypertension. Prolonged state would be anything beyond an hour or two for the average person. Ive been in this boat and suffered some cardiac complications, and that was only from excessive caffeine use while being bradycardic an hypotensive with orthostatic hypertension. Its almost impossible to distiguish when something serious is happening or if it is simply anxiety. If you are doing meth you are at risk of a cardiac trauma. With physical exercise ones heart rate typically returns back to normal quite quickly. Stimulants of any kind force the heart to work at an excellerated rate for hours without producing the hormones that signal the body to rest.
Generally it is recomended that when palpitations persist during rest for 4 hours or longer its time to get checked out in hospital. I would think that it might be a good idea if you suspect you might have anything to worry about. It doesnt hurt to verify if it is anxiety, or if the meth is still affecting you and to make sure nothing serious is going on. With a simple EKG and some blood work you can at least alleviate some of that anxiety
If you arent feeling better or if this happens again, I really hope you get checked out.