I've tried installing and uninstalling optifine, I've tried turning on and off the experimental rendering. I have no idea why I am lagging so hard when using create .3.1, some help would be nice because I love this mod, and also this update.
(I had 40 fps when using .3, which for me is good, but now I can only top out at 7/12 fps.)

Hmmm your pc should be able to handle everything just fine. This might be a shot in he dark, but try disabling threaded optimization for minecraft

What cpu and gpu do you have? (If you don't know you can upload a screenshot with F3 open) Other people have been having similar issues. Also do you still get this lag in a fresh world?

i get this lag in a fresh world, with no create blocks whatsoever

Alright, i tried that, but it didn't do anything. Is there anything else i could try?

Any other mods installed? I found similarly bad lag with AiImprovements in my singleplayer 0.3.1 create test world, but if it is the case of an interaction between our create and aiimprovements i couldn't explain why..... But first: logs could maybe help, mc complains sometimes if something takes too long. And second, a modlist. If you do have AiImprovements installed, maybe try switching of entity multitreading (did it for me in my pack).

well this is really confusing me, i tried removing the water mods, and even with all these solutions i still lag hard?
edit : after removing the water mods, i did get a frames increase, from like, 1 / 3 fps, to 10 / 12 fps.

alright, the mods i have are
appleskin
create
dynamic surroundings
entity culling
farmer's delight
fast furnace
fast workbench
fast leaf decay
fluid physics
immersive engineering
inventory tweaks
jei
mantle
mixin's bootstrap
mousetweaks
optifine (HD_U_G7)
placebo
saleable cat's force
water erosion
tinker's construct
sound filter's

Are you near the ocean?
Is the config for fluid physics mod have ocean water infinite enabled?
If not, then this's obviously the one

Also with water erosion as well, the combination would be obviously destructive

hm, i'll see if thats the case, lets hope it is,

Maybe try and install Spark ( https://spark.lucko.me/download ) and run the profiler ( instructions ) then paste the link here, should be able to work out what is causing the low tps at least. (which should hopefully fix fps as well)

https://spark.lucko.me/BLSblTOpdg
I did this without moving or really anything, just standing there, don't know if that does anything or not.

hm, i'll remove it and see what happens.

it didn't do really anything, should i do another spark thing now that it's gone?

Sound Filters is pulling a third of your tps, but that shouldn't be causing that much rendering lag...

i think i know what the cause of it is, something to due with Nvidia, i tried to set up vr minecraft a bit ago, and now even vanilla minecraft is hella laggy. so that must be it.

I cant replicate this, but I have noticed that something called blaze3d is taking up a lot of tick time in yours but not in my instance Here I can't figure out what it is from googling, although it may be Minecraft's rendering engine or smthn similar.

That seems strange, if you change the directory of an instance does it still lag? Or is it just in the one where you tried to install VR.
I'm pretty sure curseforge has a fix option that re-installs a modpack, you could try that as well.
Another spark thing now that Sound filters is gone should help as well.

alright heres the weird thing though, its every instance of minecraft, no matter what i do i cant escape the lag.

Could be a bad java installation, try re-installing java or installing Open J-9.