Feeling nervous

Hello to all! FTM here. I have PCOS so I’m not sure exactly when I ovulate but my cycles are around 30-36ish days. My LMP was 03/28/20 so based on that when I had my first scan I would have been around 7weeks + 3 which due date then was 01/4/2021. My period for April never showed. I tested April 26-28th & all negative. I didn’t get my first positive until May 7th, so again assuming I ovulated late. My dating scan was on 5/21/20 and I was told I was 6weeks + 1 or 2 (the tech wasn’t 100% sure) instead of the almost 7weeks +3 there was a HB detected of 124bpm. My due date then moved to 01/13/2021. The CRL was only .35cm which is small from what I’ve been seeing? Is it possible baby is just measuring small or is that normal? I went to the ER Sunday 5/24/20 due to some cramping and pain in my back. I had an ultrasound done and the doctor said baby was okay but measuring 6weeks + 2 days. Which moved my due date to 01/15/2021. I’m just confused again FTM so I don’t know how any of this works. I just hope baby is doing okay. Thanks for any feedback!