Could I be pregnant? All info about cycle included.

Mandolin
I am 7 days late for my period, my usual cycle length is 28-30 days long, and I'm currently on day 42 of my cycle, and I had unprotected sex on days 17 and 25 of my cycle this month. 
I took a pregnancy test a couple days ago, when I was only 3 or 4 days late, and it was negative. I'm just a littttlle confused. I'm not having any period symptoms, other than the occasional cramping, but no spotting or blood. I've been peeing quite often though. Other than that, nothing. Indigestion too. 
I am 17, so spending $10-$15 every time I have a pregnancy scare is not ideal. I just wanted to know if anyone had any ideas. Thank you!!