If both your T and Pdoc agree that you should file then do so, They have a long paper trail of mental instability that will show your constant struggle. You don't need to involve a Lawyer until after you first filling for it and If you need to appeal then contact a lawyer.

As for age I was a few months shy of 44 when diagnosed Bipolar and my Chronic physical pain and it took me 4 years to win my case. So the sooner you apply the better.