What Causes Delay In Menstruation Other Than Pregnancy?

2 weeks ago 1 week before period was due I got period back and thigh cramps which is normal to get the day before my period so I thought my periods early but I never got for the next week a got twinges in my stomach both sides mainly my right side tho increased hunger then day I was due my period it never came im now 5 days late and for 6 days have had constant period cramps in back and thighs. Could I be pregnant? I have taken 2 hpt both negative. Currentl yhunger has gone back to normal. Sore throat that keeps coming and going for 2weeks now