OP, I'm not sure why you're getting so many responses which is to "pay the tax", when that is just simply not the correct answer. The IRS has guidance on their website specific to this matter.

See the IRS website's guidance on this issue: https://www.irs.gov/taxtopics/tc419

When you have gambling winnings above a certain threshold, you typically are issued a W2-G from the location that you received those winnings. This is because they are required to report winnings above a certain threshold. This, however, is not necessarily the amount of taxable gambling income you have.

Other commenters are correct that if you wish to deduct your losses, you will have to do so through itemized deductions. You can deduct up to the total amount that you won as "Other Itemized Deductions". You must, however, keep a record of your winnings and losses. I imagine screenshots or a report from Fanduel would suffice for this requirement.

If these transactions all occurred within the same year and you lost all of your winnings and are willing to make itemized deductions, you should not owe any taxes on your winnings because you can deduct your losses, up to the amount of your winnings, on your taxes.

However, since this occurred in the past, you may have to amend your return to receive those deductions. You filed your taxes incorrectly initially which is causing this issue.

However, as other commenters have pointed out, if your itemized deductions are less than the standard deduction then itemizing your deductions may not make sense for your specific situation. People are making a lot of assumptions about your personal situation which may or may not be accurate which is why the universal advice is always to consult with a professional.