keep (going) on about (someone or something)
To continue or speak for a tedious or exasperating length of time. My date kept going on and on about his charity work, never even asking what I do for a living.
keep (going) on about someone or something
to continue to talk excessively about someone or something. I wish you would not keep going on about Tom and Jill. Don't keep on about my haircut. It's perfect!