You should never stop taking a heart medicine abruptly or without your doctor's knowledge and approval. It sounds like the medication is not agreeing with you and so have a talk with your doctor about alternatives. There are so many other heart meds available; no need to feel so miserable.
A simple blood test will let you know if your potassium levels are low. In the meantime you could try eating a banana a day and see if that helps. If your levels are way low, the doctor can take care of that as well.
You should NEVER trust advice about medications you get on forums. If you ask this question to a cardiologist on expert forum, he will probably answer that he won't give advice on meds, and neither should lay people like us.
I 100% second Ireneo and her opinion on letting doctors handle your meds.
It seems you have some kind of bradycardia (slow heartrate) and your BP is low. I don't think hypokalemia causes low BP and heartrate, anyway, hyperkalemia combined with low heartrate is possibly dangerous, and you should figure this out ASAP (if there is a reason to believe you are low on potassium). Most likely there isn't. Every electrolyte imbalance should be corrected as soon as you can, though.
Correction: Hypokalemia combined with.. (the point was correct but mis-spelling)