why is my rabbit trying to get out

Please, serious answers..

He doesn't do it all the time but I have seen him at the corner of his cage scratching like hell and biting around the bottom and corner. I looked up rabbit.org and although it didn't specifically have this issue it had some similar and I would be only guessing it's sexual frustration?? He puts his head in the air and rubs parts of his cage with the underside of his face. Something else he does, happens frequently, he thumps hard with his back feet, usually when he's out of his cage. What does this mean?

When in doubt ask the professional. I have been raising rabbits for 24 years.

When he rubs his chin around the pen he is marking his territory. Rabbits have scent glands under their chin and this is how they mark their territory. Many other animals do the same thing.

Regarding the scratching, do you have a solid floor cage? If so, that is part of the reason. Rabbits won't so much with a wire floored cage. If you have a sheet of any kind in the bottom of the cage such as newspaper this would help explain the biting at the bottom of the cage and corner. Rabbits like to bite and pull at sheets if they are in a cage. Scratching helps keep their claws short and sharp. Biting on stuff helps wear their teeth down and keep them sharp. Rabbit teeth grow 1/2" per month, so they need worn down to keep them at their proper size. It's good to keep a small block of non-treated pine wood in the cage for them to chew on.