Clear blue weeks estimator

Hi all, 
I'm 5.5 weeks and took a clear blue digital weeks estimator test last Friday--it said I was 3+ weeks, then tested today and it says 2-3 weeks. I'm concerned because I will get my blood taken on Monday to test my hcg levels, but have been somewhat spotting. Am I looking too much into this? Anyone else have this happen to them? Thanks!