Hiiiiiiiiiiiiiiiiiiiiiii! I actually don’t usually rec fics because I am super unorganized about my reading, I never remember titles, etc. I’M SO SORRY. but I do have a few long-ish omega harry fics:

lemon eyes by turnyourankle

the ‘harry, you little shit’ series by juliusschmidt - it’s not technically complete, but it’s 15 stories together of almost 90k words

all these lights by mediawhore - i’m not sure if i’ve read this one? but it might fit what you’re looking for

no easy love (could make me feel this way) by anon 

for detailed fic rec lists, check out @nottooldforthisship and @softhie. also @theficpusher does themed recs, though not all larry, so maybe they’ll take a suggestion for omega harry? you could send them an ask.