Welcome to Just Answer.
Sorry to hear about your problem.
Bricks that are chipping or falling off, along with the mortar, means that the integrity of the chimney is breaking down, from weathering. If left alone, it will progressively get worse. The best thing to do, is to fix it as soon as it is noticed.
The mortar is usually the first to weaken, with age, and crack and fall out of the joint. This is the ideal time to replace the mortar (called repointing) because the surrounding brick can be saved.
If the weakened mortar joints are ignored, eventually the brick will weaken, due to contact with excessive water, ice, etc. The bricks will begin to spall (crack and chip.) As this gets worse, the only option is too cut out the bad bricks with a masonry saw and replace them. It can be a very dusty, messy job. Full bricks can be mortared back into place. I would not use any other method as a fix, such as banding, because the chimney will still continue to get worse and allow water to leak into the house.
If you are not comfortable with working at these heights, then I would have a few masons provide a quote for you.
If you need further help or clarification on this answer, please do not hesitate to reply to this post.
Thanks for asking your question at Just Answer.
Best of Luck, Brian
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