Gillekens debuted for OH Leuven in the 2014–15 Belgian Cup in the sixth round match against Kortrijk, a 3–1 loss.
However, that season he was part of the reserves and only fourth goalkeeper behind Logan Bailly, Yves Lenaerts and Senne Vits.
During the winter 2017–18 transfer window OH Leuven signed Kawin Thamsatchanan, captain of the Thailand national football team and soon thereafter, Gillekens was demoted to reserve goalkeeper.
Following Thamsatchanan's injury during the 2018–19 season, Gillekens again became the first goalkeeper for a few matches before being surpassed by Laurent Henkinet.
After being a free-agent player for a few months, Gillekens was signed by Mouscron in the beginning of November 2019, as their first goalkeeper Jean Butez had suffered a long-term injury.