I agree with others that you should definitely check in with your doctor and seek some further resources for working with professionals that address eating and nutrition.How do I fool my brain to release its grip and accept other food when there is nothing else it wants?
It sounds like there may be a significant emotional component here, namely anxiety and shame. I certainly don't deny, disbelieve or downplay your physical experience - but also, I think a certain kind of anxiety related to eating can grow very rapidly and start to control our entire diet. Working with a mental health professional to understand and manage anxiety better could possibly help your eating issues.
I don't think you should feel any shame, but I'm guessing you know as well as anyone that surviving on ice cream for 9 months is not a healthy option for you. So, in your case, this issue deserves your full attention. I don't think having intense phases of eating the same thing is a problem, but it has to be something that meets your basic nutrition requirements.
While you are in this phase of ice cream, perhaps you could get yourself to also drink some sort of nutritional shake or at least speak to your doctor about how to get essential vitamins and minerals.