Continuious period and pain
My period started on 22/02/11 it usually is quite heavy and lasts 5-6days max. this time it lasted 8 days then a thick brownish red discharge followed on some days turning red and slightly heavy then going back to brown with almost bitty pieces in it, on day 16 its gone back red and is like I'm starting a new period,today is day 18 and its as heavy as day 2 of a normal period,I keep getting stabbing pains and cramps I am 44yrs old and usually quite regular with a cycle of between 23 and 28 days but the past 6 months it varys between 37 days and 16. What could this be? In the past I has several (5) abnormal smear tests but haven't had one since 2009 even though I was told I should have one yearly because of my smear history, please help.