Could I be pregnant or just late

Heather
Last month I started my period 9 days late due to a recent move from Ohio to California and I'm assuming stress had a lot to do with it 
My last period was September 3 and I am currently late again 
We did have sex during the fertile days but used the withdrawal method 
So I don't know if I could be late due to my period just being slow or maybe I am pregnant 
I am not on birth control and the only signs I am having or have been having for a few days now is my breast feel heavier and loom larger and my back has had random dull aches 
Whenever I am about to start my period the day of I have severe back ache first and stomach cramps 
The back aches I have been having come and go and feel like period ache but no period 
Any advice 
I was suppose to start a few days ago but I'm on cycle day number 33