See IRS pub 504 on Alimony starting on page 12. If your divorce was final after 2018 then Alimony is not taxable or deductible.
Ask your lawyer to pay any penalty or interest for not reporting it.
For a divorce that was finalized on or before December 31, 2018, alimony is taxable to the recipient and deductible to the payor, and this was not changed by the new tax law. In other words, the new law does not automatically change the tax treatment of old divorces.
For divorces finalized on or after January 1, 2019, alimony is not taxable to the recipient and is not deductible to the payer.
(If you have a divorce that was 2018 or earlier, and it was modified after January 1, 2019, the alimony is still taxable to the recipient and deductible to the payor unless the modification expressly says that the new rules apply to the modification. For example, you and your ex might ask the court to enter a modification that would reduce the alimony payments in return for making the new rules apply--your ex pays less but does not get a deduction, and you receive less but don't pay taxes on it.)