I've been lifting pretty much my whole life, but recently I'm getting this weird tendon/ligament pain behind my armpits.

It only happens for pushing motions, not pulling. It doesn't matter if I'm lifting 45 or 265, but with more weight if I push through I start to get tingling in the same area. Resting from bench, etc. hasn't helped. If I do push through it for a few sets, then it mostly goes away for the rest of the lift.

Can't find shit about it online.

Any ideas on what it is and what I can do about it?

rotator cuff?

Go see an orthopedic Dr specializing in shoulders. It may just be tendonitis. I have had both rotaor cuffs torn from lifting. Don't ignore it, it won't get better on its own.

Do physical therapy for 4-6 weeks, if it doesn't get better schedule an MRI.

Don't think so, I've had some rc injuries and this feels completely different, plus both sides are the same. Almost like a cramp or something.

But yeah, guess I'll have to go to the dr. if it won't go away.

I wouldn't discount a few nasty knots in and around the scapula.

I have a few that require pretty regular attention, and when they really get tight it sends pain all over the place, could be up my neck, down the outside of my arm, could make a shoulder pop while pressing.

They are stupid.

This.

Get it looked at by a specialist.

What i thought was a shoulder issue was actually deterioration of a couple disks in my neck. It's pinching a nerve bundle that shoots out to the arm.