Hi Tamara
Actually, I have no idea why I capitalized “mon”. :shock:
Maybe I just wanted to give you your due respect? 
amy :lol:
Or you could also say, among other examples:
I can’t but ask.
I can’t help asking.
I can’t avoid asking.
I just have to ask.
I just can’t resist asking.
I can’t refrain from asking.
I can’t suppress the urge of asking.
I can’t get over my compulsion to ask.
I can’t resist the (nagging) compulsion to ask.
Yeh, Hon 
P.S. (Hon Yeh is a real mathematician, by the way).
P.P.S. Thank you, Torsten and Conchita, for your first aid