Change all passwords of your accounts, social media, windows, browsers, emails, etc., and where possible enable 2FA (2 factor authentication), and use the function to close all sessions in all devices.
Uninstall all browser add-ons for the time being. IF you have a browser account enabled, check it doesn’t reinstall those add-ons. Enable the “Clear browsing data” function for everytime you close your browser, at least until you are sure your accounts are not compromised.
Enable 2FA for WhatsApp and and select the option to close session in all devices.
You don’t need to install a 3rd party antivirus. If your computer has Windows 10 or 11 and it’s up to date (version 22H2 at least) it will have Windows Defender. It’s all antivirus you need. Stay away from Norton and McAfee, they are not so good now in 2023. If you insist on getting an antivirus try BitDefender.
You say you reset your computer. See thoroughly if maybe you are using a cracked application or game, don’t install it yet, hold on until you can be certain it is not compromised.
If you have remote support applications (TeamViewer, Anydesk, VNC, etc.) don’t install them yet.
Disable Windows remote assistance (you can find it using the search bar).
When you reinstall applications, download them from their official pages, not 3rd party sites (like uptodown, softonic, filehorse, etc.).
Do the same with your phone, maybe it could be compromised somehow, specially if your main WhatsApp is there. Do a factory restore and don’t install all your apps yet. Don’t use apk files to install applications if possible or get them from reputable sources.
Be wary of links sent to you in WhatsApp or your email, check twice what you are clicking.
If you have your Windows system linked to a Microsoft account, do not restore your backed up configuration when you link it again to your computer.
My suggestions are:
Hope this tips help you.