Lagging out of nowhere

I rely on our internet to work from home and my son does competitive gaming. 

I am connected via ethernet and for gaming it was wifi.

Everything was working fine until about a month ago when we had the little black standing box for the internet. It would go down while I worked and while gaming the ping would be out of control up to 200 when normal was usually below 50 via wifi.

We never had any issues before besides occasional outages. So this was sudden and went on for over a week. 

So I decided to upgrade a few weeks ago to xfi gateway hoping it would fix the ping issue but it didn't. The ping is worse and it doesn't matter if connected to wifi or ethernet. Ping will go above 50 and pass  200 which never ever happened before. 

We just had the 2 week test and received the emailed results that said everything looks good. 

Now for gaming we are remaining connected via ethernet but the ping is still sporadic and doesn't remain under 50. 

Why would it all of sudden change so drastically when we never had issues before?