Going Back on Property Issues

My question is how long in Louisiana is too long to go back on property distribution after divorce? I have been divorced for eight years now. We were married for 7-1/2 years. When my husband and I divorced, I had been through so much emotional turmoil from family deaths and then issues concerning the reason for our divorce, that I could not think clearly. I also could not afford a lawyer at the time (and no one would lend me the money to get one), although he was the one who filed, and he had me help him make up our own property agreement, which excluded me from getting any of his retirement. At the time, all I was really concerned with was having a place to live since I had such a low paying job and could not think clearly enough to be able to get a better job. I was on anti-depressants and was barely functioning. As a result, I signed a property agreement that stated that I would get the house only with no retirement from him in any way and I got no alimony since he would be helping me to finish paying for the house, at which time, it would be signed over to me. My lawyer at the time that I was having the ownership of the house signed over to me told me that I was entitled to 40% of his state retirement that he gets from working at a prison and that he took gross advantage of me because the house and land were not worth as much as I would have gotten had I gotten a lawyer. Is it too late now to go back and ask for some of his retirement, especially since the outlook for my retirement (what with the low-paying jobs I've had) is grim? The family doctor that gave me the antidepressants is retired and no longer has the records I assume.