|Just to add:|
Trying another browser is useful because it will tell us if it is a browser issue or not. We can then tackle the problem without necessarily keeping the alternative browser,
As regards malware, MalwareBytes is very good and often finds what your anti-virus can miss. However this one (ADWCleaner) is focussed on browser malware and can even find what MalwareBytes misses:
(blue "Download Now" button on right).
Download and "Save" the file somewhere. Go to the saved file then double click it to run the program. Use the "Scan" button, followed by the "Clean" button.
It is best run before MalwareBytes. Please keep all logs.
Always pop back and let us know the outcome - thanks