Severe ping and relay issues, can't play WvW anymore

I am writing this kind of sad because I am realising I can't play my favourite game mode anymore. Usually in WvW I get about 50-200ms ping, which is acceptable to me and doesn't interfere with my gameplay too much (I am playing on a WiFi connection, which hasn't changed in any way for the past year). Recently in WvW I am getting an average ping of 400ms, which spikes up to 4000 (!) during large fights, and my relay response also dips into red and goes as low as 5-10, meaning my skill won't register. Today I had a truly bizarre connection issue in WvW where I was showing as disconnected and couldn't use skills, but could talk to people in chat.

This hasn't always been an issue. Even just 1-2 months ago I could play fine, with perfectly playable connection even in zerg fights with a full map Q on each side.

Why is this happening? What can I do (also, sadly a wired connection is not an option)? I read ArenaNet switched to some cheap Amazon servers a while ago and it has been giving people problems, is that true?

I'm not sure Amazon servers are 'cheap', but some time ago the game did migrate to Amazon servers.

Have you tried using a VPN?

I am having the same problem for the last 2 weeks or so. I play from Brazil. Where I usually play with 200 ping, now I get get an average fo 600, with 1 or 2k spikes.