I have just had an antibody test, they can detect the antibodies for up to 12 months
My wife was convinced we all had it around new year - it certainly knocked me for six and laid me up in bed for a few days
Result
Negative
The NHS recon the online antibody tests are not at all accurate, which is why they recommend not buying them.
With regards to what you had around New Year, according to my doctor, there was a nasty flu like virus going around between November and January which make a lot of people think they had CV19.
I had that bug (when I was at Centre Parcs of all places), but compared to what I had in March I'd take the Centre Parcs bug all day every day.
The Centre Parcs bug (as I'll call it) was done and dusted with antibiotics in a few days.
What I think was CV19 took me over 3 weeks to clear, and even now I have a lot of the after effects confirmed CV19 patients are displaying (breathlessness, headaches, aching muscles etc etc etc).