Had diarrhea, vomiting, stomach cramps 3 days, now my ribs hurt when breathe deep, pain goes up shoulder & neck. Why?

Ribs hurt. Just as severe coughing (typically from asthma) can cause your rib muscles to ache, repeated vomiting can do the same thing. The other possibility is that this probably viral illness that you had may have inflammed the lining of your lung, which causes a sharp pain on breathing in called "pleurisy.".
Vomiting. If you've been vomiting for three days, then you likely have some musculoskelatol soreness in your ribs, shoulders and neck from the exertion. I would suggest you seek out a local do for some omm to help hasten your recovery.