I got my BFP 3 days ago and im now getting cramps!?

i would just like a bit of reurance that in early pregnancy you can get period cramps....i am only due on today but i have the cramps, not severe just normal dull ache and tensing feeling, i am not bleeding and i feel fine apart from tired and sore bb's, i dnt usually get sore bb's before my period just slightly sore .....i think im just worrying as we have waited so long for this BFP, when should i get concerned about this cramping?