Hi I Am Having Menstrual Cycle Issues, My Dates Keep

Hi I am having menstrual cycle issues, my dates keep changing.. After my second child I did not have periods for two months and then went normal but now they are delaying too long, and no I'm not pregnant. Could you please help me, I use to have periods end of the month and since last few month moved to beginning of month, last month was delayed by few days and now it's over two weeks.. I get period symptoms but yet nothing