This could be Cyclic Vomiting Syndrome. It usuallly happens in the late night early morning hours...with mine, i wake up with sudden severe nausea and an urge to have a bowel movement...usually starts coming from both ends by this time, but the vomiting is intesne. bile every 5-10 minutes and no relief from the nausea inbetween vomiting spells..the stomach cramping is another typical symptom. you may also drool excessively(unable to swallow your own spit anyway, all of the acid from the vomiting will ause severe acid reflux. I lost my teeth by the time I was 25 due to all of the acid eroding the enamel on my teeth. I have also been diagnosed w/ IBS-C and gastroparesis, but i have just had to try to ID my triggers. It cqan be set off by such things as positive stress(holidays/events) or negative stress. Too little slep, overdoing yourself...fatty food..I would definitely get a thorough GI work up and if everything comes back"normal" it could be CVS. . The hot shower is also very telling. Some patients(quite a few) get much relief from a scalding hot shower. I pray that you find the answers and get relief.
Hello and welcome to the forum. That's such a lot that you've been through with this health issue. Please work with a gastroenterologist to determine cause and treatment plans. Yes, this could be a manifestation of IBS. IBS can look different and take different paths with different people making it a little bit of a difficult condition to diagnose. But essential to do so. They have many medications to help. Are you losing weight with the current situation? I do want to point out that one can become so constipated that they have impaction in the bowel which could lead to vomiting. You do need to be evaluated for this right away if you haven't already. Please give us an update.