My period only lasted 3 days and is always 7or more.after it ended came headaches, stomach cramping, tiredness, dizziness also. could i be pregnant?

Possible: It is not uncommon for women to experience bleeding in early pregnancy that is mistaken for a period, especially if no contraception is being used. The tiredness and dizziness are common symptoms in pregnancy, but in many other conditions as well. Do a home pregnancy test, perhaps two, and go from there, treating your symptoms as needed. Best wishes!