My phone wont switch on after I accidentally rebooted it please help

i have bought this micromax canvas doodle 3 2 years ago it gave me a good experience but from lat month it wa behaving wierdly and now today when i started using whatsapp it ea gone white screen and i accidentally hit the reboot button and waiting switch on by itself but it wont it never did and ive taken a suggestion and pres the power button and volume button for long time it wont work pleae give me another suggetion