Due date confusion from digital test & last period

Ashley
I'm a little bit confused I was in the dr May 4th for my Pap smear a pregnancy test was taken then which was negative. My last period was April 9th. I took a clear blue digital 5 day early detection test two days after my missed period and it was negative this was May 11th. On Sunday may 22nd I took another test just to see and it was positive just a cheapy test. Monday the 23rd I took another clearblue digital and it said 3+ weeks. 
Im confused why the 1st test didn't read that I was pregnant and then just 11 days later it was 3+ weeks. Does this make sense? Or could my hcg levels just be high?