First ultrasound measuring a week earlier than estimated. What does it mean?

Reposted because my first post won’t let me edit for some reason sorry😅 but someone said on the first post that I ovulated later than I thought which does seem possible, but I’m still confused because if I did ovulate later than I thought, (some time AFTER Feb. 6th) how did I get a positive pregnancy test on Feb. 13th? Is that even possible? Counting from the 6th I guessed I was only 7dpo which is still VERY early but would be even earlier if I ovulated later right?

First post👇🏻

So ive been tracking my cycle (only my period not ovulation) for the past 6ish months and my cycle usually ranges anywhere from 32-52 days long. Idk if I would call it “irregular” but it can be some months. My last period was Jan. 18th-21st which is shorter than it usually is, my app predicted I ovulated on Feb. 6th, i didn’t have sex that day but I did 2 days before and found out Feb. 13th that I was unexpectedly pregnant. Going off my last period I was estimating to be 7 weeks 5 days when I went to my first ultrasound but after the ultrasound they said baby was measuring only 6 weeks 5 days so a whole week behind what I thought. Is that a bad thing ? Does that mean I ovulated sooner or later than the app predicted or could something be wrong with the baby? I have low progesterone and had a miscarriage last year because of it but have been taking a prescription for it this time to help.