"I feel exhausted, struggle to concentrate and find myself procrastinating.." That sounds like the problem. Not that you are 33 or your co-workers are younger.

"I feel exhausted, struggle to concentrate and find myself procrastinating.." That sounds like the problem. Not that you are 33 or your co-workers are younger. You should find out what is up with the concentration and procrastination, take steps to address that, and forget about age. At 33 I don't think that is the issue.