Should I test?

So my "period" started 5 days ago. But it has only been spotting (brown). The last 2 days I haven't had to wear a tampon, and there is nothing when I wipe. It's like I'm not even on it. My periods are regular, and usually not very heavy. But, I've never had a period THIS light before. I'm just wondering if I could be pregnant. Also, my boobs usually go back to normal once my period starts, but they have stayed fuller this time. I also have had really bad insomnia. I know just taking a test would tell me, but I don't want to get my hopes up. And don't want to waste a test! Any one have something similar and turned out pregnant?