I'm Only 42; Should've Already Had My Period First Week

I'm only 42; should've already had my period first week of Dec, however this week would've been the latest since my periods shift from the first or the third week, but it is regular. I have read on symptoms etc on menopause etc; not too sure if it's me yet. I've had tubal ligation about 15 years ago. I am not feeling any other symptoms yet to be concerned otherwise. Any other ideas?