The pill

Angel
So I started a new pill about a month and a half ago, this pill does have a chance of stopping my period. So this month I didn't get a period I had a little spotting and that was all, but how do you know if you aren't getting a period due to the pill or if it's pregnancy? I just don't want to have to keep buying pregnancy test but seems like that would be the smartest thing to do.....?