I was overhead pressing on my 3rd and last set of 135, on the last rep I tried to push it up in a strict manner, I got it up to about my forehead, it want budging, so I let it back down and switched to a push press for my last rep. I got it up, and locked it out for about 5 seconds, let it down, and re-racked it, 5 seconds later I felt a sharp pain in my spine right in between my traps, where the gap in the muscle is. Is there a way to fix and prevent this? Here is a picture of where the pain is. BTW I'm 15 years old.
I had a similar experience when overhead pressing. My problem was deactivation of the core, causing instability. The problem is amplified by heavy load causing poor form. Before pressing brace your core tightly.
What I did : I do GermanVolumeTraining (10x10, 60 second rest) standing dumbbell overhead press. Concentrate on bracing the core and keeping the body stable: not deactivating core, not locking out knees and keeping hips slightly bent. Hereby activating the whole body.
Notes on my experience: The high volume (100 reps) helps with developing good motor patterns, developing stability, and increase muscle mass. You'll notice that using 3 kg dumbbells the first week will be sufficient. If you can (with good form) perform all 100 reps then it you would typically increase the weight. It is important to start with a light weight to learn good motor pattens.
At 15 I don't think you should be performing heaving over head press without a good coach. Injury is one of those things you'd prefer not to learn by experience. Please be safe. Happy lifting.