I can't progress on lifts once I hit a certain weight. I can do a billion reps at n pounds but n+5 I can't do a single rep. Wtf do I do?

I also don't lose fat when I starve myself. I usually lose a few lbs then maintain weight on like 600cal. I feel myself getting weaker but I stay soft

get those tiny change plates that are like 0.5lbs, and just increment with those