While it is likely that you have had at least one concussion while playing football, I don't recommend a self assessment. I would recommend talking to a medical professional and getting some tests done to rule out any other issues.
If it is post concussion syndrome, there is a good chance that they won't find anything in the tests, yet you are still experiencing symptoms like Mathew described earlier. And yes, they can come on later in life.
For treatment, I highly recommend CranioSacral Therapy (CST). I have used CST for over 15 years to treat various stages of concussion recovery. It is a very gentle and effective therapy to assist the healing of brain trauma; even if that trauma happened many years ago.
The Upledger Institute has actually been working with the Ricky Williams foundation in a program that helps former professional football players from the NFL and Canadian Football league suffering from concussions and post-concussion syndrome. The positive results we are seeing from these programs are measurable and have been published and presented at a Brain Injury Conference.
Please feel welcome to contact me with any questions you may have.
Best of luck to you on your healing journey.