In 2006, Lewallyn began his baseball career in sales and public relations with the New Orleans Zephyrs, the Triple-A affiliate of the New York Mets, before becoming a pitching coach with the Pensacola Pelicans professional team of the American Association. With the Pelicans, Lewallyn worked with former major league pitchers and had two of his players sign contracts with major league organizations. In the fall of 2008 the New York Mets sent Lewallyn to Arizona to attend the Major League Baseball scouting bureau's scout school program, where he learned the process of evaluating amateur and professional talent. In 2009, Lewallyn returned to the Panhandle Conference serving as the pitching coach at Northwest Florida State College. 

In August of 2010, Lewallyn joined the University of South Carolina Beaufort as assistant baseball coach and oversaw the Sand Sharks first ever draft pick in program history in right handed pitcher Dexter Price, who was drafted by the Arizona Diamondbacks. Lewallyn took over as the Sand Sharks' interim head coach in November 2011 and after leading the Sand Sharks to a school-record 41 wins, winning the NAIA opening round tournament and earning the first NAIA berth in his first season, Lewallyn was officially named USCB's Head Baseball Coach.

In 2012 Lewallyn was recognized as the Diamond ABCA Regional Coach of The Year for the NAIA as well as the Rawlings NAIA Mid-Atlantic Region Coach of The Year. Lewallyn also oversaw the highest draft pick in USCB program history, Michael Heesch was selected by the Chicago Cubs in the 8th round of the MLB draft as well as being named The Sun Conference Pitcher of The Year.

Lewallyn compiled 162 wins in his five seasons at the helm of USCB making him the winningest coach in the program's brief history including 4 Sun Conference tournament appearances, 3 NAIA Opening Round tournament appearances, and 1 NAIA World Series appearance. In 2016 Lewallyn was named The Sun Conference Coach of The Year and led the Sand Sharks to the first regular-season Sun Conference title in program history. The Sand Sharks also set a program-record with 44 wins, climbing as high as No.5 in the NAIA Baseball Coaches Top 25 Poll, and qualifying for the NAIA National Championship Opening Round for the third time in five seasons. 

In his tenure at PSC, Lewallyn has accrued a record of 151-171. The Pirates won the Panhandle Conference Championship in 2020-21.

Lewallyn received a bachelor's degree in Business Administration from the University of Central Florida. His father, Dennis, was a pitcher in the major leagues with the Los Angeles Dodgers, Cleveland Indians, Texas Rangers and is currently a minor league pitching coach for the Atlanta Braves organization. 

Lewallyn lives in Pensacola with his wife, Emily and their daughters, Ellis and Maggie May.