Ive been feeling strange upper abdominal pain since last friday after getting my pfizer vaccine. the past two days ive been having some odd leg and pelvic achiness (feels like period cramps but im not on my period). any idea whats going on?

While "upper abdominal pain" is not a common side effect of the Pfizer vaccine, "leg and pelvic aches " can occur with either Pfizer or Moderna vaccines. Some who get vaccines may also have active relatively non-symptomatic COVID infections which have not been detected, which also may produce vague muscle cramping secondary to the affected nerves by the virus.