No DNS address assigned??

I have had consistent outages for at least 2 months, some last a few minutes some last for days. I've gone through all of the troubleshooting suggestions. I've even replaced all of my cords, checked to make sure my modem & router are compliant and even bought a new computer last week. Everything is set up for internet settings to be assigned automatically but it doesn't assign a DNS address. I've even taken note of the DNS address the 2 minutes my internet is up and tried to put it in manually but that's not working either. I work 60hrs/wk, some of it from home and this is REALLY a problem for both time consumption and work. Help!