your computer acting little funny can have different reasons. most likely is some Windows update not installed correctly perhaps.
to check if your computer could be infected you can run a scan with mcafee.
to do so;
on the taskbar you see ^ this icon.
if you click on that icon there are some icons overthere aswell from mcafee.
if you click on the mcafee icon you see several options aswell a scan option
go for full scan and your computer is being scanned.
if the outcome is O infections found at the end of scan your computer can be considered safe.
if you have a new AV product and is not Mcafee and you want to use this new AV you need to remove first the current Mcafee version from your computer.
when it is removed Windows has its own AV called Windows Defender that will take control in the meantime for protecting your computer.
in the following article is described how to remove Mcafee AV from your computer;
McAfee KB - How to remove McAfee products from a Windows PC (TS101331)
use option 1 and when done do a reboot for your computer and use option 2 after from the article aswell.
hope this helps answering your question