High Latency/ping spikes; laggy online gaming

Hi for the past month or so I've been having a really bad experience trying to game online where lags really bad to the point of disconnecting sometimes. I've done speed tests using different websites and speeds seem to be fine but when using latency tests to different servers on testmy.net I get wilding fluctuation results. Ping has even gone into the thousands before so something is definitely wrong. All tests were done connected to my router via ethernet and again connected directly to my modem and the problems still persist. Could someone help please? I also have screenshots of modem stats if it will help but not sure how to post images.