Can anyone help with the maths because I’m a little worried about my dates and terrified this pregnancy will result in another loss.

Last period 11/11/22, cycle averages around 36 days.

Had a terrible illness mid-December so had no sex at all after 4th December 😂 then had a bit of spotting on 20th December, which I presumed was the start of my period but I got 4 positive tests instead. Could implantation have occurred so long after conception? My positives aren’t that dark either which has me worried about my hcg levels. I have a lot of symptoms but all very mild and kind of what I would expect in the run up to a period anyway (apart from being way more tearful and not very irritable)