So gals and guys, let me kindly give my opinion. I know you are trying to help but I am sensing what might be construed as hostility in the comments. I think hersweetleaf could use some more compassion here than "you screwed up". We've all fallen for people who are maybe not the best for us. It is in getting to know them better that we discover this. Sometimes that discovery is painful.
Bottom line is those of us that are really new to poly just need guidance and support. We are most prone to making mistakes and our relationships are usually the most vulnerable. Any of you out there that have found third partners and are keeping everyone happy (or at least generally content) at this point in time should count yourselves lucky. The rest of us are just out there investing feelings in people that don't work out.