Why is my period 19 days late?!

if you generally have regular periods, and you are sure it cant be pregnancy, reason may be low percentage of body fat. Everyone tells fat is bad. But a woman's body need a minimum fat level. If it is less, periods stop immediately. Many supermodels have this issue. If you are not extra thin, you may be anemic. You can try taking iron tablets. If that is also unlikely, you should go and see a doctor soon.

Old wive's tale : eat lots of papaya, pineapple, sesame seeds, dates. periods will come soon

Have you been stressed out lately? That may be it. I have heard it is normal for menstruatal cycles to skip a month, once in awhile.

have you been stressed out recently or put on/lost weight? or are you on the pill and messed-it up a little? these are usually triggers for periods being late/not at all :)