I've never played for basketball for an original team a day in my life, could I still walkon to a D2 college ?

It's possible. The fact that you have experience in football is a plus, and you must be really strong if you were able to play DE at 5'11''. You would probably have to be a defensive minded PG in basketball, and you could probably take advantage of smaller guards by backing them down into the post. It's never too late, but you would have to really bring your A game to prove yourself as a walk on at a D2 college.