If i am not pregnant, what are the causes of these changes?Everyone reply kindly...?

it is very normal coz many a times women even if everything is going well may miss their periods......may be u eat less or less of diet and consumption of unhealthy food can make ur uterine lining thick and then it takes times ti thicken and more time to fall off as periods........so dont worry...wait till ur next periods and if the same thing is observed then see a dr..........:) good luck!