Any one any ideas what this could be??!?

ok so i came onto my period on sunday -- over 2 weeks late! been having a lot of problems though (if you wanna know see my other questions!) and thought i might have been preg but obv not! since i came on though its been stop startin...like bleeding one day then not the next then like the next morning but not all afternoon etc etc...have also been feeling doubly sick and have been quite a few times!! does anyone have any ideas as to what might be going on?? would go to the doctor but everytime iv been they say its nothing to worry about and im a bit fed up of it really so...any ideas please?? what could be making things like this?? thanks xxx