Is it normal to sleep up to 18 hours a day with out waking up?

i can sleep up to 18 hours a day and sleep very very heavy people find it very very hard to wake me and i have 3 young children that my partner has to wake up and deal with them as i am sleeping so heavy i dont hear them i can wake up after a 16 hour sleep and still be tired and want to go back to sleep is this normal and is there any thing i can do about it