“My father is from Ireland and my mother from England. I have been traveling from the U.K. to New York for over 10 years on the visa waiver program. I never overstayed the 90 days. I play pool for a living and have won many national and international tournaments, mainly in the U.S. I have also been on ESPN playing in a televised pool match. I have an apartment with my girlfriend in Brooklyn.
“I was recently refused entry into New York under the program. Officials said I have been using it too many years and spending too much time living in New York and playing in pool tournaments without the proper visa.
“I spent eight hours in the immigration room at Kennedy Airport, then five hours in a cell there. I then was sent home on a flight the next day. I'm now in London staying with my parents trying to figure out what to do to get back to New York and my girlfriend.
“I have been getting letters from tournament organizers and companies like ESPN supporting my case, stating that I am a world class player and that I am needed back in the U.S. for future tournaments. I don't know if I should go the sports visa route or the marriage/fiancé visa route. Any advice would be appreciated.”
The first and by far the most important piece of advice is this – you’re going to need the assistance of an attorney who practices U.S. immigration law. What follows in this column is a general overview of your situation, but you’ll need to discuss specifics with an attorney in order to figure out the best way to proceed.
Of course, as you likely know, the U.S. Customs and Border Patrol officer you encountered at Kennedy was correct in detaining you for continuous, long-term travel to the U.S. using the visa waiver program. As you’ve been using the waiver for 10 years, it’s surprising that you’ve only been detained now.
The visa waiver program allows for short-term (up to 90-day) visits to the U.S. without having to first obtain a tourist/business visa. Those using the waiver must depart the U.S. prior to the 90 days.
Waiver holders can engage in limited business activity provided that no income, save for expenses, is received from a U.S. source. From the information you’ve provided it seems as if your primary source of income comes from pool events in the U.S. This is definitely not permissible under the waiver program. 
And even though you never overstayed the authorized 90-day period of entry and visitors are allowed to avail of the waiver program for multiple entries, the officer who denied you would have seen your frequent travel pattern over the past 10 years as an abuse of the program, especially with regards to your career as a pool player.
What to do next? You seem to have made a name for yourself in the world of billiards, so perhaps you should look into the P-1 visa, which can be issued to an internationally recognized athlete. An immigration attorney can help determine your eligibility for the visa.
Presumably your girlfriend is a U.S. citizen, as you also mention the K-1 fiancé visa. You would obviously have to commit to marriage in order to make proper use of this visa, and that’s a question that only you can answer.
The K-1 visa, when issued, allows the fiancé of a U.S. citizen to travel to the U.S., and the marriage must take place within 90 days after entry. Then the foreign spouse can apply to adjust status to that of a permanent resident (green card holder).
Having a green card allows for more freedom and options than a P-1 visa, and it’s valid indefinitely, as long as the holder adheres to its provisions. (P visas, with renewals, are good for up to five years.)
Be advised, though, that the K-1 visa can take several months to issue. P-1 visas can be applied for using the premium processing service available from the U.S. Citizenship and Immigration Service (USCIS), for an additional fee of $1,000. This guarantees service within 15 calendar days after the application has been received.