trouble maintaining internet connection for TV

We have a Panasonic 2014 Viera (smart) TV and like to watch Amazon prime and Netflix. Over the last month we have had repeated problems with the download speed. We cannot watch a show in HD, and last night at 8pm we could not watch anything on Amazon prime. We have the preferred package and should have adequate speed. I just checked the speed on my laptop PC and it clocked at 36.6Mbps. What is the problem??