my period has lasted 9 days and still here after being late 11 days?

my period is always regular i mark down when im due every month and it always comes when i expect but this month my period was 11 days late?? i thought i was preg? but my period fnally came and after 9 days it is still here ?? my period normaly lasts no longer than 5 days ? but the strange thing is its been totaly diffrent from my previous periods? started with dark brown blood ? and continued all through with the same sort of blood ? i usually only get this at the end of my period ? ive done a home preg test with negative results ? i have signs of eing preg but not the result on the test to verify the same ? can anybody answer me as to why this is happening to me ? my first and last preg was nearly 8 years ago ? and i have been trying for a second child ? i just don undestand this months period ?? and help would be great :/