couldn't help doing的问题

couldn't help doing的问题 can't help to doing 和couldn't help to doing一样吗 Suprised at it, we couldn't help doing. I couldn`t help couldn't help I couldn't help i couldn't help but " I just couldn't help can't help but doing,can't help but do ,can'help doing的区别 cannot can't couldn't mustn't的问题 can't help doing can't help but do 和couldn't help but do 只是时态的区别吗?