Weird recurring pain in arm pit, what could it be?

Hi! A few months ago while I was driving home on a long road trip, I got this sudden, very strong pain in my arm pit (weird right). It hurt to move my arm in any direction, and even when I kept it pinned against my body it was still pretty painful. I had no rashes or any sort of outbreak on my skin, lumps or anything. It got progressively better over a few days then went away so I just dismissed it. But lately it has been coming back, pretty frequently. The area still looks totally normal, and I don't feel any swollen lymphs or anything. I tried googling it, but any armpit pain info I found was associated with an outbreak of some kind. Any ideas what it could be? Thanks so much