Tomorrow will be 1 month since I had a type 2 SLAP repair w/ decompression. As soon as 12 days after surgery, when I began PT I had no pain and ~90% ROM. As of yesterday at PT I had no pain and 100% ROM UNTIL the PT had me stretch by walking my repaired arm up a wall and leaning into the stretch. Doing it facing forward was painful and when I switched to doing it sideways I about jumped out of my skin. We continued with the rest of the session afterwards, but my arm was sore. Fast forward to last night adn today and I am in SO.MUCH.PAIN, especially if my repaired arm is bent and rotated internally. Oddly enough, if I let it hang or extend it externally, the pain goes away. I don;t see my OS until 7/2, but I do go back to PT this coming Monday 6/25.

I like to think that I have a pretty high pain tolerance, but this is ridiculous. It hurts more than my injury did before surgery!! has anyone experienced this? Is this pain due to to not really using my arm in this manner much since I injured it? I expect some pain, but the good 'I just worked out too much and I'm awesome" pain, not the "oh my lord please amputate now b/c that will fell better than this" pain.

It is not uncommon for PT to be painful when you first start out. I can't speak for slap repairs, but cuff repair was terribly painful. If you have any meds left, now is the time to help yourself. It will get better.
Luckily I am prohibited from doing anything at all that even comes close to the point of discomfort or pain in PT. But that just makes it a very long process, which is OK, I guess
Hang in there, one month is a very brief time in the shoulder recovery world - it is an alternate universe with a different clock.