Monthly Period. Some difficulties?

Hello Doctors! Myself Anushiba Sen. Age-27yrs 8months. In general my period date is around 22nd to 24th in every month and this is so very regular from last 1year.. My in this month (September) it's already 29th and it's late for 6days as on my monthly regularity dates.. I am unmarried and there is sexual intimation as I am single. Before the days of my circulation sometimes I feel fatigue, pain of lower abdominal portion and so on but this month I have feel nothing yet also my haemoglobin level is so low it's now 7.2. In the previous month it was 6.2 and I consulted with one of Haematologist and she prescribed me for a IV iron Injection which one I took... Can you please tell me is this 6days late of my menstrual circular is considering as normal or this is gonna create some difficulties?