Suffering flickering issue once game is launched

[Sunlit Queries]

With or without Optifine 1.12.2, I continue suffering a white flickering primarily on the top left quarter of my screen. It occurs far more frequently when I am moving my mouse and also affects all pause/option menus, but only if the game has been launched. (I.E. does not affect title screen.) It is a multiplayer server. How do I diagnose or fix this? I believe my graphics card is 'amd radeon rx 5700 xt' or another similarly powerful Radeon graphics card. I have 8 gigabytes of ram dedicated to the game (16 gb ram on computer) and the modpack requires 5 gb.

 

Sorry if this is in the wrong area! I could not find a more optimal place to put this post, as it is my first one here and I am not experienced in forums of any kind.

Edited December 27, 2019 by Sunlit Queries
Clarification on my newness

[Munaus]

moving this to Cafe Lame, as Mod Makers market is for discussing how to create mods and not how to avoid flickering.