Help me please.

I live with just my dad, and my period is extremely bad, I'm 17 years old and I've had my period for about 6 years now and it's always been the same except for the past year, it's very irregular and never comes on the same date or near the same date, and it's EXTREMLY heavy and I get cramps that hurt so bad it makes me sick to my stomach, sometimes it will last 4 to 5 days and other times 9 days. And I don't know what to do... (My mom isn't in the picture so that's out of the question, and my dad is in the military so he isn't home very much so we stay with my grandma and I think it's weird to bring up and  makes me very uncomfortable. )