dependent on pacemaker

Dear Sir,

I was implanted with parmanent pacemaker on 05 Aug 2007. That time it was told by doctor that my PM works while
I am sitting/standing. But in lying condition my heart is pacing normal. I was implanted with make Biotronik, model
Philos SLR which works as double sensing and single pacing. Last Month when I have gone to program my PM, the programmer first done the ECG without Magnet and then with magnet. then he told me that I am hundred percent dependant on PM. My question is :

(1) What Will be the effect?
(2) What may be the cause?
(3) wheather I can regain the earlier condition?

Somnath Banerjee