It doesn’t sound like you ever developed good study habits, since things came easily to you in HS. One of my kids used a reward system for herself – after finishing a study task, she’d give herself 15 minutes on her phone or a snack or something. She went to the library every weeknight (even Fridays for a while before going out).
No one can give you self discipline. You are going to have to find ways yourself to monitor and reward yourself for getting your work done.