Nothing on 6 week ultrasound

I went for a scan 10 days ago and nothing showed on my scan only free.fluid in two seperate spots in my.uterus today at 6 weeks accord to LMP i went for another one and was just told nothing was seen just a collection whatever that means the tech was very abrupt and wouldnt tell.me.if they even seen a tiny sac.nothing now the thing is usually i have a 28day cycle but in june i had one.for 4 days starting 9th june and then another one started 20 days later on the 29th june for 12 days is it possible.i ovulated really late i just need some reassurance