Who knows what your condition really is? Esp over a forum.
I’m just throwing ideas at you.
There could be a million reasons why. One guy i know, used to be a great Middle distance runner, ran a 35min 10km also. Could not handle sprints volume at all. He has since stopped and can bench 200kg now.
His body nervous make up is not suited to short sprints - tis why i mentioned it.
Im not so crazy to say “THIS IS YOUR PROBLEM” Just giving you an example.
Could be
sleep
nutrition - not just volume of food, there is a million things in food that make you feel crap.
Stress
chemical stress
emotional stress
Postural alignment issues
ect ect
Your best bet is to find a Top Level coach in person and get him to figure it out.