I am taking 2.5 ng of bisoprolol when i lay on my back my heart rate drops to 55 bpm from 66 bpm and i get missed beats is this a problem ?

Not surprising: Bisoprolol is a Beta-blocker, and these work partly by slowing the heart rate. When one stands the heart rate usually increases. Conversely, when one is lying down, or relaxed, the heart rate is generally slower. As long as you are not feeling dizzy or lethargic, the heart rates that you mention should cause no worries. Good luck !!