account password

Got an email from LIfelock that my. info was spotted on dark web. Trying to change my password for CC. It's not hard. But, it never takes. I am sitting waiting for a confirmation msg on the screen that the change took place. It never comes so I am using my old password. Lots of spam email lately & strange activity on my computer. Always on the comcast email page. When I try to sign out of my email, it does not sign me out. Instead I get a crawler from the bottom of the page in red "servor unavailable." My nephew, IT peraon, said that should never happen. Also, once when I signed in to my email. in the upper right hand corner (above "SIGN OUT"), there was an email address that was not mine, my name was not there. Another name was. I am getting very concerned about my online safety. What can we do to resolve this serious problem.