Need help for bit sync in CPFSK demodulation

Hi,

I am working on CPFSK modulation and demodulation. Please find the below details about fsk

 It is a non data aided (no preamble/sync byte) 2 fsk with continuous phase. The data rate is 564 kbps and the two frequencies are 3.951Mhz  and 4.516Mhz with +/- 200Khz tolerance.

I am getting fsk modulated data in cyclic manner continuously till the passive tag is active.

So i am using non-coherent correlation based demodulation scheme and with this i am able to demodulate data but some times i am getting bit errors when the two fsk frequencies are changing with their tolerance. So i wanna use bit syncing algorithm for this, please suggest a bit syncing algorithm.

Please let me know if any further details are required.