Very Slow Download Speed compared to normal download speed?

Hello, I have the Preferred (50 mbps down, 10ish up mbps) internet plan. Normally realistically I get around 38-43 down and 7-9 UP.

About a week ago, my Upload speed was completely fluctuating and eventually stayed at around 3 until it recently fixed itself. (During this time, the download speed was not affected what so ever) .

HOWEVER, NOW the UPLOAD speed is perfectly fine, but the DOWNLOAD speed is super low. Normally get 43ish, right now Im lucky to get 10. If I use the internet speed checking on cox internet, its fluctuating quite a bit but still staying around mid-high 30s (used to get 40-50 on cox internet speedtest). When I use normal speed test Im lucky to get 10

. I'm starting to believe that the problem is the Modem/Router I'm using which I'm borrowing from Cox with $$. 

Any Help would be appreciated . If need any more info, i'll be glad to supply.