Messed up belly button - what are my options to fix it?

There is only one surgery that can correct your belly button. A full abdominoplasty, aka tummy tuck.

Dear mirandagrant,
based on your photos, you look like a good candidate for a TT. Full tummy tuck should tighten your abdominal muscles and remove the excess skin. Flanks liposuction would give you a better shape. I would suggest you to consult a board-certified plastic surgeon because only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Thank you for your question and series of photographs.  Nothing replaces an in-person examination, but I think you would most benefit from a full tummy tuck and liposuction of your waist and flanks.  The tummy tuck will tighten your stomach muscles, helping to achieve a flatter appearance, while removing excess skin and adipose tissue that is weighing down on your belly button and causing the horizontal shape and skin overhang.  Liposuction can be used to enhance your tummy tuck results by narrowing your waist and removing isolated areas of diet and exercise resistant fat. Hope this helps.

Appears as excess supra umbilicial skin that can be corrected in a full TT surgery. Best to seek in person or virtual consulations. Fees range from $8,500 - $18,000.