Malware: Consulted Xfinity provider, downloa Ad Block Plus, start up still slow w/solid screen...hel

I'm a "semi-techie" with some experience with computers and classroom experience with computers interested in learning more through community experience rather than classroom.
 
I unfortunately clicked on the right menu within my Facebook acct. introducing Malware to my home laptop. As my screen buzzed and furiously flashed and buzzed, I read the request to call an 888 phone number; I immediately shut down and called my provider who advised I download Ad Block Plus and scan with malware bytes.org. After getting rid of the flash/buzzing, I now start up and each time it seems slow to start with a gray screen to begin with. Though I've scanned frequently, I can't help but think there's still something hanging onto my computer. Possible? Any way to further research?
Many thanks for any help you might provide,
Sue Wonder