Time to sit and talk. Looks like you need to state your need to not feel excluded--and I'd extend that to needing some sex play that doesn't involve fetish play. Negotiating getting your needs attended to generally won't break a relationship, unless the others involved simply don't care (and then you wouldn't want to be with them, anyway).
Next, I'll also suggest that you begin dealing with your insecurity, as that will bring down a relationship. I'll suggest a book called "Ten Days to Self Esteem" (it's a workbook) that helps you sort out what you're doing to feed your insecurity and how to change it. From here, I don't see a grain of truth in any of your numbered points above, and I suspect you'll be able to sort that out before long and realize that you're beating yourself up without cause.
So, while waiting for your book to arrive, sit down and talk about your feelings and what you need, sexually. I'll suggest that having everybody involved in having sex at the same time every time probably isn't going to satisfy everybody non-stop. You may want to have sex with husband #1 alone, with husband #2 alone, with just the two husbands, with just the wife, with just the wife and #2, or the wife and #1 or any combination thereof.
You may want to experiment with some forms of BDSM play to find out if you enjoy any of it. You'll also want to negotiate having regular non-fetish sexual play to make certain you're getting what you need. The only way you'll get what you need, however, is to advocate for yourself to get it.
Keep your stick on the ice--we're pulling for you.