You can use ClamXAV for mac free from App store
or sophos free download for home users
Now wait for some users to state there is no need etc........ (Can of worms opened) lol
Sophos I have been using and have had no problems
Do a repair permissions
If you search more like this for Macbook pro running slowly you will find many answers
Malware is not remotely the first thing you should think of if your machine is having problems. It's almost certainly not malware. Most likely, you have installed some bad third-party software that is causing the problems. See my Mac Performance Guide for some help troubleshooting those issues.
As for the virus issue, if you really want to do a scan, I would recommend Sophos. But note that no anti-virus software is capable of detecting all malware. See Mac anti-virus detection rates, as well as my Mac Malware Guide.