I am afraid the mode of injury doesn't quite fit in with sub acrominal bursitis.
Add to this that sub-acrominal bursitis is most (90%) of time secondary to supraspinatus tendon irritation.
The correct management after 2 months of pain is take an x-ray.
There is also a need to do this because of presence of the joint subsiding under load. The AC joint also needs to be evaluated for separation and the capsule can also be investigated by taking measurements.
After this a correct management can be established.
If everything is ruled out and correct tendon or concomitant complications are correctly diagnosed - then ultrasound therapy and shock-wave therapy should remedy the condition in about 4-6 weeks with 10-20% improvement every week.
Hope that helps,
I am afraid we are based in Wimbledon which would, maybe, too far to travel for you.
Niall Marshall-Manifold D.C
wimbledon Chiropractic and Sports Injury Clinic