Fitting in fitness

I study full time 9am-5pm monday to friday and then work night shifts 5.30pm-10pm most nights too. In the weekends I play sport on a saturday morning then usually work. I’ve noticed I’ve started to put on weight and really want to go to the gym more. I have a membership and I’m paying for it but never go! I’m always soo exhausted late at night when I get home that even waking up extra early to go I’m extremely tired and unmotivated.. anyone have any tips or motivation that will help me find a way around my tiring life?