Skinny Bowel Movements, belly button pain, upset stomach

I'm a 24 year old male. Last Saturday night I noticed pain in my belly button after eating Maryland blue crabs. I didn't think anything of it, as it felt as though I may have just bumped into something. This was a celebratory weekend and I had drank somewhat heavily the night before, as well as the following night. The following afternoon the belly button pain was worse, but not to the point that I felt I needed to do something about it. Later that evening the pain felt like it was spreading towards the right, so I feared appendicitis and took a trip to the ER.

After an examination and CT Scan, the ER doctor told me it was possibly an umbilical hernia, however he was unsure of anything and discharged me.

The following day I had a very skinny and difficult bowel movement, but again, didn't really think anything of it. However, after dinner on Monday night I felt general nausea and discomfort, moreso than I have felt in the past. I woke up on Tuesday morning to loud gurgling noises and feeling in my abdomen (not sure if it was stomach or intestines) so I made an appointment with a gastroenterologist. He too was unsure of what was wrong with me and assumed constipation, prescribing me Hyomax (supposed to reduce intestinal spasms) and metamucil. He also said he did not think I had a hernia.

After 2 days of this treatment my symptoms have gotten worse. The belly button pain has dissipated, but my bowel movements have all been very skinny (pencil thin) and difficult to push out, and I have had increased abdominal cramping. Nothing that has been unbearable, just uncomfortable. I've also had muscle pain in the lower right part of my chest near the sternum. I called my doctor back and he wants me to get another CT scan.

Does anyone have any idea what this may be? Could a bad crab have caused this? I appreciate any feedback anyone can give me.