Default nexus 7 dosent boot to bootloader

i was using xperia rom,but unfortunately bottom of the touch has broken making it irresponsive.i had to flash another rom.so,i flashed non-touch CWM recovery flashed rom and gapps via sideload.after successful flashing it rebooted got boot animation then it restarted itself,said optimising apps again rebooted.thought of installing another rom.entered bootloader selected recovery from then on it only displays only CWM logo at center of screen and restarts.now am unable to boot it to bootloader...tried removing the battery pins,but still the same problem.
CURRENT DEVICES
DELL venue 8
HTC PICO
PREVIOUS DEVICES
HTC SENSATION XE
XPERIA X10