Is this normal

On May 13 I had a blood test done and it came back negative. I had some spotting for a couple of days and thought I had my period. Yesterday May 20 I was still having symptoms but they were stronger and thought I’ll take another test first thing in the morning. This one came back positive. Could it be that I have low hcg levels and it’s just now showing up? My LMP was March 30. I’m having another blood test done on May 26. Did this ever happen to anyone else?