[968rz]

I too had shoulder pain when reaching up when I was an auto tech (15 years ago?) Being the man I am I waited till I couldn't use it any more due to the pain (took about 8 months).
Turns out all the over head work caused the end of my collar bone to hit the shoulder bones (micro injuries they called it).
Tried about 2 months of PT and drugs with no change so I had to have surgery. They removed about 1" of collar bone (ac joint resection) followed by 6-8 months of PT and it feels great again.
I learned my lesson then and 5 years later when the other one started to ache a bit I rushed in. Sure enough had to do it to the other shoulder, this time they did it arthroscopic - faster recoup but never 100% like the other one.

Go to the Doc and find out what it is and before it gets worse.
(FYI: I saw the one of the bills for the first surgery and it was well over 60K, luckily it was all covered under workers comp as I was poor then)