It looks like you've got a nerve problem, probably a result of postural misalignment. Have you ever had any
back pain, or numbness down the hip of the same side as your piriformis problem?
If you have any current video of yourself running or racing, see if your head-neck-hips-feet are in a straight line from side profile. If any of this is out then the hip and back take a beating, and this soon spreads to legs.
I don't think racing is a good idea now. The fact that the track turns hurt your coordination means that your body is not in balance. Any race you run will not be any where near a plausible reflection of your fitness. You've got to get this fixed.
If you can still train, my advice would be to focus on good posture above all else. Perform short reps with the aim to hold form and not to muscle your way to a good timing. If you are stil unaware of what is good postural alignment, I would suggest consulting a trained therapist or knowledgeable coach/trainer before continuing to hammer yourself to the ground for a season that might not materialise.
On your own, try doing core work with focus on getting the basics right. Too many kids say they do "core training" on their own, or during school practices, but many are not activating the correct muscles, just physically mimicking the action that is required using mainly the limbs. (I'm not saying that you are necessarily guilty, but just a word of caution to every one reading this....)
If you go on "Flotrack" and see some of their workout videos, you will find that some clips featuring college athletes doing conditioning work are examples of poor execution,esp exercises like plank where many 'cheat' by using more their arms and legs, with the trunk slumping and neck dropping.I've seen this happen way too often, esp when the coach is not around.
Years of core training done poorly does nothing for the athlete unless you consciously translate it to your running itself. Do not asume that just because you have done it right and done it right several times, that you will automatically have good running form, or even optimal daily posture.
Again I use Seb Coe as a good example. From nearly all of the races that I've watched him run, he would always be focusing on holding good posture, EVEN WHEN HE WAS LOSING THE RACE. Why? Because good posture means optimal movement mechanics.
If you read "Better Training for Distance Runners" in the chapter on biomechanics, The writers mention that Seb Coe worked for 3 years during his mid teens to correct his bad mechanical habits. No doubt the process wasn't totally ended then, but he took those years to get at least the basics right before the great WR performances came.
Watch the ending of the 1984 Oly men 1500m final and contrast Cram's 'walking thro mud' form versus Coe's balance and symmetry. Cram was tired and chose to compensate, with his head looking down, arms flailing, body twisting. Where have you ever seen Coe drop his head down and twist his body and arms like that? More often he would choose to keep good form and seemingly slow down and either watch his rivals pull away or overtake him, rather than muscle his way towards the finish line. If you compensate every time you do a hard workout or run a bad race, it becomes programmed into your CNS and this becomes second nature. Pretty soon the injuries will come.
Finally, if you get your info on core training from the internet or other publications, make sure you read every instruction carefully. Understand which muscles are required and not just assume. You can get injured by doing core work wrongly. Just going thro the motions helps nothing.