Period or pregnancy

I am new to this ttc and I am only 3 months in but it seems like I am just not sure if this month could be it. I have had sore breasts, what I think is nausea, but not sure if it's all in my head or not. I have been tired but not sure if that's been because I have been busy. I did notice my boobs feeling fuller, but like I said I am not too sure if it's all in my head. I am supposed to get my period 9/17 and I am just not wanting to test too early. Any suggestions?!