8 weeks and still don’t see embryo

Hi, my LMP is 17th May, so by right I should be 8 weeks now. But my period usually delays for about 1-2 weeks (~40days cycle), and I did home test on 26th and 27th June, both negative. I tried again on 28th June and only then I found an ultra faint line. I had a scan on 8th July and doc said the sac is still too small, looks like 4 week size. I got a scan again on 14th July and doc still unable to find embryo, and suggest me to wait for another 10 days to get another scan. So while waiting I’m super anxious now. Is it because my cycle is longer so the LMP calculation method is not accurate?