You can use Smart Touch. Go to settings>accessibility >smart touch.
It's a hardware problem. Visit your nearest service center.

My back touch button stops responding very often, then it’s fine again.Also many times it registers 2 “clicks” instead of 1 when I touch it.One strange thing is that sometimes when it cames back after the dead period it clicks itself quickly many times,like 10-20, maybe for the times that it wasn’t responding before

Leg or something maybe?