is calling an ex cheating?

i have a new bf who ive been with for 1year now, though at night when im alone i get the urge to call my ex, on occasions i call him on a private number and he always knows its me and calls back. when he calls back i made up lies saying i never called and then just hang up and go on with my life, i dont want to get back with him but i always feel i have to call him to know he still cares.