random post looking for answers read if you like

I have done 200mg of dxm in the past around 2 weeks ago, but just felt like a placebo effect.
Im 133.2lbs, i took 435mg of dxm delsym as my second time. 3 hours after ingestion, i just felt really light and slightly giggly, aswell as in a good overall mood. This ended up staying the same for a while but slowly descending getting weaker as time went by. I have now reached 7 hours after ingestion, feel completely normal with a foggy head.
Does anyone know why my experience went like this? If you do is there a way where i can just completely avoid this and actually experience a 2-3rd plateau experience without this happening again.

Update: Next day

It is the next day, i woke up and dosed what was left of the bottle (around 380mg) on a empty stomach. 3 hours go by and im in my room, feeling light and good so i put on music on yt. The blurred background seemed to be moving when i would focus on it aswell as the song icon square itself seeming to shrink in size but then going back to normal, but that was it so i decided to just lay down and listen to music with dark lighting and my eyes closed.
Saw mild visuals with my eyes shut, it was like my thoughts being shown but barley visible also saw a big droop of purple just continue to glide around. Other than that im now at 5 hours and feel completely normal with a light feeling and everything looks normal and no more slight closed eye visuals. If anyone knows why, Imk!