Should I still test?

My period was 6 days late I took a pregnancy test on the second day and it was negative I was going to take another one this morning but last night I started spotting it lasted maybe an hour and then stopped completely even after I had sex (tmi sorry) still nothing... and now today the same thing just happened again I spotted a little for an hour and then nothing again... I'm having my usual PMS symptoms that started the day I was supposed to start my period and my periods are usually regular... I assume this is my period but my sister insists I could still be pregnant and should take a test because spotting can be normal.....But I don't want to waste the time or money if it's just most likely my period....what do you guys think?