I dont want to scare you mate but that type of pain sounds very similar to the pain i had.. and im now 4 weeks post SLAP op with 4 anchors.
Remember, just because you still have good strength in the gym and ROM is fine does not mean something more sinister isnt going on. I could still do snatches, military press, pullups, deadlifts etc etc etc after my injury. It never hurt when i was in the gym.. just a dull ache afterwards. And i never had any problems sleeping.
I did mine doing shoulder press and bench. I have my own opinions on kipping, personally i think its a rediculous movement, but thats just me. Ive lost count of how many shoulder problems ive read about from people kipping.. but anyhow.
Get it checked out asap mate, at least then youll know exactly what is wrong. The money youll spend to get an answer is well worth it.
All the best.