Bullets 'n' Babes

My internet is quite sluggish but my PC appears clean.

I currently have installed...

Comodo Firewall
Avast Free Anti-Virus
Malwarebytes' Anti-Malware
Housecall

Do I need anything else?

A strong mind to resist suspicious porn sites

Comodo Internet Security Premium is the only thing I have.

In other words, sorry, can't help.

I only have ESET for work and because it is one of those expensive attach itself to inner workings of your system it is quite effective, but also slows things down (regardless of how it advertises itself.)

Now to tell what is slowing your system down if you are using windows (you wrote PC so I am suspecting this): go to the Task Manager, Processes tab and check what is hanging on the CPU column -- aka what has a high percent (for example for ESET it is the ekrn.exe which shows under the Image Name.)

HungFist wrote:A strong mind to resist suspicious porn sites

That's something I don't have!

Iobit Advanced System Care is a beautiful program for optimising your PC.