Was i under paid for my settlement?

Last year I filed an injury lawsuit against my former employer here in California, during the settlement meeting between their insurance companies attorney and my attorney I was initially offered $1500 at which point my attorney asked that we speak outside. He told me my injury (slipped disc in lower back) was considered to be somewhere between category 2 and category 3 and that it could take up to 5 years to get me maybe 8000. However he wouldn't tell me how much I should ask for, he just said he'd ask for whatever I say but he couldn't give me an actual suggestion as to how much I should ask for so I proposed 5000 and the insurance Company agreed. However many people since have said I should have got more. The insurance company was also supposed to pay back around 2500 to disability for benefits I had received so far, disability claims they only received 1500 from the insurance company, who now refuses to speak to me because they want my attorneys office to call but the attorneys office refuses to because the case is over and they no longer work for me. So my question is was I underpaid? if i was underpaid is there anything I can do to pursue action against my former attorney for failing to inform me? any help is greatly appreciated.