The last sentence of your opening comments was ..... how can i tell if i have malware so here are a few checks you can do.
1. run dxdiag
2. run windows memory test , it will tell you if ram is faulty but not which stick
3. check device manager for any yellow triangles.
4. use task manager to see what is running in background.
5. look in add/remove for anything you dont recognise.
6 look in reliability monitor and google any errors.
7. run scans with malware bytes , anti virus and widows defender , all 3 look for different things.
8. when downloading something make sure you are on the makers website and not a 3rd party.
9. be careful when typing as hacker rely on people making spelling mistakes , 2 examples trivagio ( extra i in the name ) will not book a holiday it will empty your bank account , malawarebytes ( extra a in name ) will not give you the genuine program it will give you something to trash everyhing on your pc.
10. BEFORE downloading something scroll down the entire web site and look for other extra bits that are ticked to get stuff on your pc that you dont want , unwanted extras use to be unticked but now sites pretick them so if your lazy thats how they get you.
11. some av like the ESET i use warn you if it finds hidden stuff during an install.
NOTE ... if malwarebytes finds anything , quarentine and delete it and run scan again till it finds nothing , this is necessary because malware stuff can be in several segments and malwarebytes does not always get rid of things on first scan
YES i have given you a lot to read but it could be useful to you.