I am nearly 13 and cant get to sleep till about 5.30am i want to sleep but i just cant help!!?

im nearly 13. Aand for the last couple of days(nearly a week) ive havnt been able to sleep untill about 5.30am wont sleep.. I have tried reading but i just drift off and sleep for about an hour then wake up to find its 4.00am im starting school again tommorow and i dont want to go with bags under my eyes and be alls leepy during school. Ive told my mum but she just finds silly excuses such as maybe yu should walk the dog more often..and excersize but I do alot of excersize actually..she doesnt take me seriously and just rolls her eyes when i complain about maybe having short term insomnia. Ive looked it up and i think i might have it..what should i do?