I'm A 51-year-old, Caucasian Female, About 40-50 Lbs Overweight. I

I'm a 51-year-old, Caucasian female, about 40-50 lbs overweight. I was diagnosed with Fibromyalgia about 8 months ago and I have been treated for hypertension for about 15 years. I take the following medications:
Amitryptiline
Tizanidine
Atenolol
Meloxicam
Pantoprazole sod dr
Hydrochlothiazide
Potassium
About 3-4 times within the last week, my blood pressure has dropped to 70/50. When my BP drops this low, I feel terrible. I get very light-headed, nauseous, and I feel drained. Usually, my blood pressure will go back up within a relatively short amount of time, but it has gone back up to hypertension level. Today I got a reading of 161/91. I also have tremors. My hands are shaking right now. I should also tell you that I have 2 other rx for BP meds. I have stopped taking them due to the drops in BP that I am having. Those two scripts are Lisinopril and Amlodipine.
What could be causing the drop in my BP and my tremors?