Is there anyway to backup current ROM without unlocking bootloader/ installing clockworkmod recovery?
I found another way to do it. This one uses Terminal Emulator or adb shell.
Open a shell as root. You first determine what device blocks /system and /boot are, with ls -al /dev/block/platform/dw_mmc/by-name. Note that the dw_mmc may vary between devices. You'll need to find it yourself. Then dd if=/dev/block/systemblock of=/storage/sdcard0/system.img and dd if=/dev/block/bootblock of=/storage/sdcard0/boot.img will backup all your Android system. 

If you want to restore using this solution: boot into recovery, mount your SD Card, then in a adb shell, do 

su
dd if=/storage/sdcard0/system.img of=/dev/block/systemblock
dd if=/storage/sdcard0/boot.img of=/dev/block/bootblock