Hi Jyoti Raina,
Your results are as expected, because when the Q-factor will go high the BER will definitely become low. and one more thing you need to be very much clear that BER or bit error rate is calculated from the no of bits that is received at the receiver (Which was transmitted from the transmitter section) by mistake or system. so for a system to be efficient it should have high Q-factor and BER as low as possible. and in you case you are getting better results. no need to worry about that. and I need to mention that you are not getting high bit error rate you can see that the power of 10 (i.e. “e”) is negative that means very low value. and BER of near to value 1 is not acceptable.
If you need further improvement in your system you can attach here with your design file so that I can have a look into it.