I took two ultracet before bed (I had only previously taken one)....

I took two ultracet before bed (I had only previously taken one). I have hypertension and takes meds (Ziac) for it. After taking the ultracet I woke at 4am and felt like I was floating. I didn't sleep for the rest of the night and got up feeling like a truck had run over me and very very tired. I felt worse as the day progressed and started taking my blood pressure which was very low. At 1pm 15 hours after taking the pills my blood pressure was 85/47. My top number was never over 100 all day and the bottom was generally in the 50's and 60's. I didn't get a normal reading until the next morning. My dr said it was because I took two ultracet. If I wasn't supposed to why does it say 1-2 every 6 hours? Has anyone else experienced low bp with this drug? I'll never take two at a time again.