UPDATE: after watching him and reading ALOT, I gave him a bath at 2am for at least 20 min because I thought it was constipation but he only pooped a tad bit in the tub and his symptoms are the same this morning. Long, deep inhales & exhales, rocks side to side slowly with each breath like he's rolling. I saw his mouth slightly open this morning which leads me to believe that it could be a RI.
What happened: during a meal he missed his 1st strike and I believe he ate some dirt. He lifted his head and opened his mouth, turning it from side to side like he was trying to swallow it. After about 10 min he went back and resumed to kill/eat. The next day I could still see the lump which is unusual, then later it looks like half his body is swollen and he's taking deep breathes.