Is the AC joint the exact area where you are feeling this? If so you probably need a shoulder rehab program. I screwed my left shoulder's AC joint up in Feb 08 going for a max bench attempt. It hurt for about 6-8 months, but I got a complete recovery out of the rehab effort & concentrating on proper form.
I highly doubt pullups or pushups are the cause here. More likely a poor-form pressing movement, or landing/being thrown onto your shoulder. For example, flared elbows with a wide grip on the bench press is what caused it for me.
Avoid sleeping on your side to avoid restless sleep due to pain.
You need to tell anyone you may grapple with that you have this problem.
Back off the weight %s you are using, focus on form. You said you may be letting form slip (but on which lifts?) and I can tell you my injury was from poor form.
Seek a push-pull shoulder rehab program.
I can elaborate if necessary.