You are having the same problem that me and others players have. Just check here:

https://forum.square-enix.com/ffxiv/...-REPLY-HERE%21

There, we are trying to understand whats happening with FF servers because so many players are having disconects, lag spikes etc. Im having lag spikes everyday, as we go into the night, the worse it gets cuz we have more players online. When I play at morning I rarely have lag spikes. I have even tried VPNs (Mudfish) but It did not work for me.

We dont know what to do, but lets keep reporting until SE see that theres something wrong wiith FF servers. Everyday more players report those disconects problems.