Nothing wrong with telling your doctor now , 10 years ago or never. It takes time to feel comfortable about telling people things and it should be understandable why it takes so much time for some people but at the same time you could probably understand why your doctor gets a little bit frustrated. If he completely flipped it he was probably wrong and it may have made you feel like you did something wrong but you didn't.

in the end, suicidal thoughts are symptom just like feeling tired or never being able to sleep, it's just that it's a stigmatized uncertain symptom for alot of people.