Chronic masterbation in toddler

My 2.5 yr old dd has been masterbating since she was a year old. At first, she would lay over large rubber balls (toys) and roll back and forth on them. Now she lays across anything she can and rubs herself against it. She is particularly fond of corners of chairs and tables. While I understand that this can be a normal behavior for young children,however, I am concerned because the behaviour can go nonstop for hours every day (yesterday it was 7 hours, the day before that 6 hours). During this time she refuses to eat or be distracted and becomes out of breath and sweaty. She screams and yells if you remove her from the object she is humping an going back to her behaviour no matter what we do to distract her. She has not been away from me ever (never left in the care of anyone else, even her father unattended) and has not been sexually abused. We have a very secure family with no stressers that I can see. She also has trouble sleeping, never falling asleep until 2AM and waking several times during the night shouting (usually she shouts 'go away', 'get off of me' or 'leave me alone' which are the same phrases she uses when we try to remove her from her masterbating), then falling back asleep. Any help would be appreciated as I believe this behaviour is no longer appropriate or healthy for her.