mega2560- Interrupts reading digital input
There isn't any interrupt code in what you posted. What exactly is the problem?  One important note is that you shouldn't try to print to Serial line in the interrupt handler as serial is itself driven from interrupts which are switched off during your handler code.  If all you really want to do is to print something every 10ms then you don't need any interrupt.  Just use the "Blink Without Delay" style of timing and keep the other code from blocking.