loud knocking

[Supra2NR]

i dunt know what happend to me this time, god doesnt like me

i was driving home last night then all of a sudden a loud knockin sound came from the engine bay, first it started when im in 3000 rpms, then it got to 2000 then lower and lower, then my car shut down while i was in the middle of the road, almost getting me to an accident

i got it to crawl into a parking lot , it wouldnt even crank, i left it there for the night

came back this morning, i got it to crank (barely) and i limpd it home, it sounds like its the pistons, i dont know tho, it sounds like its deprived of oil, cuz its really knockin hard as hell as in when you hit metal in to a bench sander,

the starting problem i dunt get since it giving me a 12v reading

the knockin i dunt know what can b causing it

so you know i have been having problems with my tranny, my gear grinds everytime i switch to 2nd, and reverse

and when i drove it the oil pressure gauge wasnt moving at all, dunt get it since i put the oil myself, dunt make fun cuz i know how to do that pls

anybody got any ideas what could be my problem this time?