>>>>Do you have suggestions on things to do so I won't be left with nothing in the long run? Is there a site that could give me more help on that? Is there a book that I could get?
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>>>I was in a similar position several years ago. I had developed software for a medical billing company and I had it copyrighted. They decided they were going to sell it to another company some time later and I told them that would be fine after they paid me. I negotiated a nice tidy sum from them before giving it to them. Of course they went bankrupt within a year, but I got out with my money and eventually retained the software. Get a copyright, then go see them.
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>>Check with an IP attorney; often, copyright is the wrong means to protect your interests; patent filings can often protect better than copyright with some types of IP.
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>I checked with an attorney, but had the copyright first. When the other side's attorney's saw that I had a copyright, they backed off. Until they learned I owned the copyright and it was displayed in my screens, they thought they were going to walk away with it.

Copyright is weak wrt things like look-and-feel issues, application of specific software technologies, and the issue of black-box reverse engineered product. FWIW, I file both types of IP assertions; the ones that generate income are broader patent issuies, which can apply to an application of a technology to a problem solution in much broader terms; enforcement of copyright is far more difficult to establish.