Weird period. Possible pregnancy. Opinions!

Hello everyone! 
I've been on a low progesterone birth control pill for the past 10years and have always had a heavy to normal period lasting 3-4 days every month. 
This month I started lightly bleeding but it was so light that I only knew it if I went to the bathroom. The second day seemed normal to start but i only bled for half the day. It has now been a week since I was suppose to "start" and I haven't had anything since. 
Should I go buy a pregnancy test? Or has this happened to anyone before?