Took morning after pill (nordette) in december and once again in february. now my period is very late? took 4 pregnancy tests but all were negative

Sound like no: It sounds as if you aren't pregnant. Possibly a hormone imbalance is occurring as cause for lack of menstrual cycle as opposed to pregnancy. Could be hormonal, due to pituitary or thyroid, or due to weight (thin/heavy). If still doesn't come for a few more weeks, consider seeing doctor to evaluate. As well birth control pills can help regulate cycle. Best wishes.