Do you have thyroid problems? Low thyroid can cause that, and it's such a common thing, it seems. For god's sake, though, don't assume you have it because of one symptom - you'd know if you did! But so many people now seem to have thyroid trouble, and it can cause really strange symptoms you wouldn't think to associate with it.
Beyond that...there's a first time for everything. I doubt it's anything to worry about, but you can always check with your doctor.
I'm guessing you're worried about cancer - don't be. Endometrial cancer causes serious bleeding. Like, you'd be worried about bleeding to death, very heavy period type bleeding. Even THEN it would be more likely to be something like a fibroid at your age.