Richmond,
I've got a long history of shoulder issues and the one thing I can tell you for sure is that even with imaging like X-Rays and MRI's... the real problems are not always easy to diagnose. It's a very complicated joint and you can have a host of things going on in there, some may not even show up on the imaging.
Just to give you an example... I've had 3 surgeries on my shoulders. I've torn my labrum twice and my rotator cuff twice. The labrum tears were quite large. In fact, the last labrum tear I had was approx. 1/4 of the way around. Guess what? All of the MRI imaging that I'd had done shown NO tears and nothing wrong. The surgeries were done because there were no other options.
Now, your AC sprain "might" be more than the doc thinks. My last injury was done snowboarding... I took a nasty fall on my shoulder and got Osteolysis of the Distal Clavicle. You can read about it here...
The Physician and Sportsmedicine: Osteolysis of the Distal Clavicle
It's hard for doctors to diagnose and it will seem like an AC sprain to them. That's what I was diagnosed with until it ended up lasting for months. With an X-Ray, my surgeon was finally able to guess that it was osteolysis. The reason it took so long to diagnose is because it can literally take a few months for this to show up on the X-Ray. It takes 1-2 years for this to heal. I was lucky and my pain was gone in 10 months.
I'm not trying to scare you, dude. I'm just telling you that there could be a host of issues going on and you can't entirely rely on imaging. I consider my surgeon to be amazing but even he got my last diagnosis wrong. It happens.
One thing that you could probably really benefit from is getting a good PT and having them work with you on
scapular stability,
thoracic mobility,
rotator cuff strength, and
soft tissue work. Working on those things could keep you off the surgery table. I would lay off the heavy weights (especially pressing) until your shoulders feel good again.