“I literally had to lift my right arm with my left arm.”
Most likely it’s a repetitive-use injury, but I did want to mention that maybe you should see a rheumatologist to rule out rheumatoid arthritis.
I have had RA for years, and your description of how things progressed with your pain sounds like my experience after long hours of anything repetitive, such as typing or painting, etc. - right down to having to lift your injured arm with the other.
Rheumatoid arthritis does run in my family. If I try to play racquetball or tennis, my right elbow is a mess next day. I get some stiffness when doing a lot of hammering or chopping also. But most other activities like running or bicycling or stacking wood do not seem to bother me.