Hey BP! I'm glad the story made you feel less alone, there are many others like it out there, sad to say. Many people just seem to totally lose their bearings at first, and then (hopefully!) come back wiser and stronger.
It's worth noting that there were some other serious issues in that situation... Eric realizing he'd never really meant it when he'd been saying he loved Jen, Jen being legitimately crazypants. There may well be a path forward for you guys where there wasn't for them. If there is, I would imagine it involves taking several large step backwards and going sloooow, keeping it light, and creating that separate space that you were missing the first time. Work towards building the trust you need to date as the individual people you are, not just as a unit, and hopefully it'll all be a little less insane.
As you're figuring out what to do, don't forget that your gf is capable of deciding for herself what's best for her. You and Elemental should of course do what's best for the two of you, and that may mean ending this relationship, but if you do so, let that be the reason, not to spare her the pain or craziness... there's nothing more infuriating or hard to get over than being broken up with "for your own good." Let her gauge what makes sense for her, and when the joy is worth the tough stuff.
The major players. Me, under-30 bi female. Gia, girlfriend of 3+ years. Clay, new boyfriend/dom. Davis, ex/"it's complicated."
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy, Clay's partner.