K.C.
Even though your mother is deceased, do you know anything about how her cycle worked? Or any of her siblings? I take more after my aunt than my mom with woman things, so maybe you can learn more about your family through any relatives that might still living.
If there is any doubt, talk to your OB. I'm sure it's not all that unusual. I feel bad for you, you shouldn't have to deal with periods anymore! Good luck, I'm sure everything is fine!