ER and admission with no resolution

I have crohns disease. I have had an ileostomy bag for six months now. For the past month, I have had extreme diarrhea and vomiting about once or twice every week or two. I finally went to the ER the last time it happened because I was very dehydrated and there was some blood in my bag for the first time.
After having a scope of my ileum and disconnected rectum they Discovered nothing. My intestines now look perfectly healthy.
My gi dr told me that the next time it happens, he will do an endoscopy. I'm so nervous because I never know when I will start getting sick. Could it be ibs? Are there special diets to consider? How can I be fine for months, and then all the sudden randomly get sick?
I am supposed to start school next week, and I've missed a few days of work off and on this past month. Any suggestions would be appreciated, especially from fellow ostomates. I have to get my life back and not live in fear of eating.

Is there any chance it could be partial blockages? That can cause vomiting or high liquid output until it passes. If your scope was normal it could be food blockages. I've only had one about 6 weeks from my surgery. My output got very watery and I was having to empty every 15 minutes. I didn't vomit but was very nauseous. Some people do vomit.

Can you remember what you ate prior to one of these times you got sick?

This sounds very similar to what I was going through earlier this year. I have an ileostomy. These sound like partial blockages, like Cupcake said above. The extreme diarrhea is your body filling your intestines with fluid in an attempt to flush the blockage out through the stoma. The vomting occurs due to your stomach filling up with food and fluid and nowhere for it to go. If it was just a bolus obstruction, meaning food just got blocked up somewhere, and it cleared by the time you went to the ER, a scope or X-ray would likely show nothing.

Granola and Triscuit crackers are very high in fiber and certainly could be giving you problems. I would avoid high fiber foods and other roughage and see if this stops happening. I would also get a follow-up scope to make sure you do not have a stricture. Tests eventually showed that I had a stricture right behind the stoma which I had to have surgically removed. My problems seemingly came out of nowhere too. It's very scary.

I've been on Entyvio for over two years. Despite my recent troubles with a stricture, they believe it was not Crohn's-related as I have no other signs of inflammation or disease recurrence. So I've been doing quite well, though I started Entyvio right after I had my colon removed so I don't know if the remission is from surgery or Entyvio. Through the years, I've had Crohn's in my colon, terminal ileum, and rectum.