Whittington attended Oakland Mills High School in Columbia, Maryland where he was a four-year letterwinner playing for the basketball team. As a senior in 2010–11, he averaged 23.5 points, 11.6 rebounds, 4.4 blocks, 3.0 steals and 2.7 assists per game, while earning All-Met Player of the Year and Howard County Player of the Year honors for leading his team to an undefeated season, finishing 25–0.
As a freshman at Georgetown in 2011–12, Whittington appeared in all 33 games while averaging 4.3 points and 2.9 rebounds in 20.1 minutes per game. After a solid, trouble free first season for the Hoyas, Whittington's sophomore year was filled with turmoil due to academic concerns. He started the 2012–13 season well, averaging 12.1 points and 7.0 rebounds in 13 games up until January 8, before missing the remainder of the season after being suspended for academic deficiencies.
Whittington failed to appear in any games for the Hoyas to begin the 2013–14 season due to a torn ACL suffered during the summer, and was later dismissed from the team on November 30, 2013. In mid-December, he transferred to Rutgers University and committed to playing for head coach Eddie Jordan. However, he caused controversy the following month when he failed to enroll at Rutgers for the spring semester, with no comment given on his decision not to join the school. Whittington subsequently sat out the entire 2013–14 season.
During the 2014–15 season, Whittington spent time with the Westchester Knicks of the NBA Development League, working out with them and practicing in order to get into the flow of the game speed for the NBA level. With his ACL still healing, he was not considered ready to play yet, thus spending another full season out of action.
In May and June 2015, Whittington took part in pre-draft workouts with the Indiana Pacers and the Boston Celtics. The Celtics' director of player personnel, Austin Ainge, said of Whittington, "He came in shape which is good. It's sometimes hard outside an organized program to stay in shape, and he did. He came in, in shape and played pretty well." Whittington ultimately went undrafted in the 2015 NBA draft and joined the Miami Heat for the 2015 NBA Summer League. He struggled in Orlando before turning it around in Las Vegas, where he led the Heat in minutes and rebounds. He also looked much more comfortable on the floor, which helped him to a more impressive offensive showing. He earned high praise from Heat assistant coach Dan Craig, with Craig saying "He's been great at getting us into second situations and then defensively, you can do a lot with him. You can switch him on the perimeters, he can rebound, protect the rim for you, and he can bust out and create breaks so he adds a nice dimension." Over nine total Summer League games for the Heat, Whittington averaged 9.1 points, 6.2 rebounds, 2.0 assists, 1.4 steals and 1.3 blocks per game.
On September 3, 2015, Whittington signed a one-year, non-guaranteed deal with the Miami Heat. He was later waived by the Heat on October 24 after appearing in four preseason games. On November 2, he was acquired by the Sioux Falls Skyforce of the NBA Development League as an affiliate player of the Heat. On November 14, he made his debut for the Skyforce, recording 18 points, 11 rebounds, 3 steals, 2 blocks and 1 assist in a 98–95 loss to the Iowa Energy. A week later, he had a season-best game with 30 points and 10 rebounds in a 98–82 win over the Erie BayHawks. His next best game came on December 4, recording 28 points, 7 rebounds and 6 steals in a 115–99 win over the Delaware 87ers. He appeared in all 10 games for the Skyforce to begin the season, helping them to a 7–3 record while averaging 15.2 points, 9.3 rebounds, 2.4 assists and 2.4 steals per game. However, a hand injury suffered in mid-December forced him to miss over a month of action. He returned to the court on February 17, 2016, and played out the rest of the season. On February 25, he had his best game for the Skyforce since returning to the line-up, recording 22 points and 6 rebounds in a 118–114 win over the Iowa Energy. The Skyforce finished the regular season with a league-best record of 40–10. Whittington went on to help the Skyforce reach the D-League Finals, where in the best-of-three series, they defeated the Los Angeles D-Fenders 2–1 to claim their first D-League championship. In the Game 2 loss, Whittington scored a team-high 17 points. In 34 games (27 regular season, 7 playoff) for the Skyforce in 2015–16, he averaged 13.5 points, 7.6 rebounds, 2.4 assists, 1.9 steals and 1.0 blocks per game. At the season's end, he earned NBA D-League All-Rookie Team honors.
In the 2016 off-season, Whittington decided against participating in Summer League activities and instead went home to Maryland to work out with his local counterparts. Such players included NBA stars Victor Oladipo and Jerami Grant.
On August 13, 2016, Whittington signed with the Sydney Kings for the 2016–17 NBL season. He made his debut for the Kings in their season opener on October 8, 2016, but struggled to make an impact offensively in 24 minutes due to foul trouble. He finished with six points, four rebounds, two assists, two steals and three blocks in a 77–73 loss to the Brisbane Bullets. In the Kings' fourth game of the season on October 20, 2016, Whittington recorded a season-high 22 points, seven rebounds, one assist and three steals in a 92–78 win over the New Zealand Breakers. On November 5, 2016, he grabbed a career-high 16 rebounds in a 64–57 loss to the Cairns Taipans. Whittington appeared in 28 games (all starts) for the Kings and averaged 11.5 points, 6.4 rebounds, 1.8 assists and 1.5 steals per game. The Kings missed the playoffs in 2016–17 with a 13–15 record.
On February 21, 2017, Whittington was reacquired by the Sioux Falls Skyforce. In nine games for the Skyforce to finish the 2016–17 season, he averaged 13.6 points, 5.7 rebounds, 2.0 assists and 1.0 steals per game.
Whittington is the son of the late Gregory and Jana Lisa Whittington, and has an older sister, Hana, and a younger brother, Cortez. Just days into his stint with Sydney in 2016, Whittington's father died after a long battle with cancer.