Bit freaked out, early ultrasound!!!

Long story short I stopped using depo shot as it made my cycles crazy. My last bleeding was the 21st Jan and finished on the 2nd Feb. I have no idea when I ovulated. Fast forward to the 24th of Feb, i got my first VVVFl, i did one every day for 3 days and they got progresively darker. I also did a digital on the 24th which said pregnant 1-2 weeks.

If my bleeding stopped on the 2nd and i got a positive on the 24th thats a period of 20ishdays in which i both ovulated/conceived and got a positive. How early it detected the HCG!!! I must have been like 1 day pregnant i swear haha

I went for a blood test on the 1st March and doctor said my hcg was 600, which he said about 5- 6 weeks ( i know doesnt add up to my bleeding and ovulating timeframe) did an ultrasound today. Did a vaginal as couldn't see anything abdominally, the vaginal could see a sac but way too early to measure...

Just wondering does this all sounds normal? Should i just wait for a few more weeks before another ultrasound. How early would i be based on the information ive given about the bleeding and positive test? Is it common to get a positive so early on in pregnancy and if i was literally only 1-2 weeks pregnant how is my hcg level showing at 600 so early on?

Please any ideas or words of wisdom bit stressed atm.

Ive attached my pregnancy test from the 1st march, 1 week after my first.. its a pretty dark line for being early on isnt it. Ive never found out this early on before so abit freaked out about it all. Hcg levels and matching it up etc