Interruption with IF

I'm trying trying to program a square signal frequency to simulate the signal obtained in
the sensor of the rpm of an engine (in the flywheel). This frequency is generated in a
timer interruption. If I don't take into consideration the two missing teeth (forget about
the bold lines in the source code) of the flywheel (60 teeth - 2teeth) the code is
working, but when I try to get rid of the two first teeth my software is doing nothing.

What could be wrong?

Thanks a lot.

#pragma RB(1)
timer0() interrupt 1 using 1
{ //takes into account the two missing teeth of the flywheel
TR0=0; //stop the timer
EAL=0; //disable all interrupts
counter=counter++; //
if (counter!=121) //60 teeth + 60 holes
{
if (counter>6)
{ //
frequen_1=~frequen_1; //invert the signal
}
}
else
{
TR0=0; // two extra microseconds
TR0=0;
counter=1;
frequen_1=~frequen_1;
}
//in case on the two first teeth I don't invert my signal
TL0 = new_timer_reload; //load the new values
TH0 = new_timer_reload_high;
TR0=1; //start the timer
EAL=1;
}