How early can I test anyway?

Dee • 42, happy mother of a lovely boy through ICSI on 3rd round. TTC #2 since June 17

So, we had sex on the 20th, 21st was the calculated ovulation date. On the 23rd and 24th I had a pain in my breast and thought I should get a breast cancer check (it’s been a while). That evening I threw up (repeatedly). This morning it turned out we had sex during my fertile window and I was just curious and took a pregnancy test and it looked pretty negative and I left it on the counter for my husband to see. When I came back from work it was still there but now I could see a very faint line. Now, I know I’m only supposed to check it within the next few minutes but now I can‘t stop thinking about it. Can I even test positive this early?!