Seems to me that you have a computer or computers that are compromised at home with either a virus, trojan or malware. Hackers have to gain access to your Cox email account by obtaining your password. You probably clicked on a link or an attachment you shouldn't have and infected a computer on your network at some point or downloaded something that was infected. Also if you plugin a flash drive into your computer that drive may have something installed that is infected. One you attach it to a computer it jumps on and spreads. This is a reoccurring problem it's most definitely a computer or device connected to your network that is infected. Change your network password as well and make sure anything wireless is using WPA2 not WEP or WPA as both of these have been defeated. Also use a virus scanner (Avast Free Version) and a malware program (Malwarebytes program) to remove the infection(s). I truly believe in your case this is a problem from your end.
Final note. Make sure your passwords are not simple and also different for each webpage etc that you login to. Every password you create should be different and difficult. Example: Ne(w)*Pa_ss[@]H*0*m*E#^𖁢 .Also you can use a the free password manager KeyPass to store your passwords.