Hi. I've been using Femilon-p tablets for over 6 months now.. from Last month I got my periods for only 2 days had abdominal pain and heavy bleeding like normal.. every time I stop the 21 day course I used to get period on the 5th day.. but last month I got period on the 7th day.. this month it's 6th day and I still did not get my period.. I took pregnancy test two times last month but showed negative.. what could be the reason this is happening.. I'm really worried.. pls suggest..