It's not uncommon for changes in diet or health to affect the way we perceive taste. And I don't mean a gluten-free diet, but any diet in general. Coffee is actually bitter, although lovers do not notice this out of habit. Are there other foods besides coffee that you have a new reaction to?
Totally agree. It's understandable that you may be upset about not finding out earlier, but it's important to focus on the present and moving forward to manage your health.