Unhappy with my teeth! Can I get a new retainer?

I am 28 years old and it is now 8 years since I had my braces removed. I wore my retainer at night as instructed by my ortho for about 1 1/2 years, and after that he was a bit vague as to how often I should carry on wearing it so I pretty much stopped wearing it altogether. Gradually over the years my teeth have moved more and more and I am now really unhappy with how they look and REALLY wish I had never stopped wearing my retainer. I have looked into getting clear or invisible braces but just don't think I can afford it and even the clear ceramic braces (which is what I would have to go for, after speaking to my orthodontist) look more noticeable than I would like. I still have my old retainer but from reading previous posts on this site it doesn't sound like it's a good idea to start wearing it again at this stage! I am wondering if there is a cheaper and easier alternative to having to get braces again, such as having a new retainer made? Would this be able to straighten my teeth out? Would it be effective if I just wore it at night, as I don't think I could put up with having that plastic in my mouth throughout the day (I have to answer phones and speak a lot at work)? Nowadays orthodontists use fixed retainers after the braces have come off and advise you to keep wearing your retainer for ever - I am SO annoyed this wasn't the case when I had my braces off :(