Your system may be infected but avg may be keeping it silent!
Malwarebytes is best choice! If it is telling nothing means you can be out of worry!
Uninstall AVG completely!
Use Avira antivir!
Avira Anvivir - http://www.free-av.com/en/download/index.html
Avira has very good internet security, real time updates, great overall protection.
If both things telling no virus means you are lucky