Diarrhea and throwing up at the same time has happened to me on many occassions. The pain from the cramping becomes so severe I become nauseated and throw up. Yes, it is hard to do both at the same time. I keep a wastepaper basket or ice cream pail beside the toilet in both bathrooms. I suffer from IBS-D. The only thing that helps is Immodium for the diarrhea and Pepto Bismol for the nausea, although my Dr has prescribed drugs for the problems. I find the OTC medicines more effective than the prescriptions and with fewer side effects.
Good luck to you. I hope you find a way to help you get some control over the problem.