Mono/poly can most definitely work, and work well. It takes effort, though, because of the varying mindsets involved - what can be "taken as read" when both parties think similarly may take a lot of discussion in a mono/poly situation.
Things tend to get even more work-intensive when you add a BDSM dynamic into the mix, because there are all of the dynamics of that to work through and resolve. Sometimes they can definitely get in the way of working through the mono/poly issues.
Adding emotional health issues into the mix and you have the trifecta - because THAT takes a lot of energy to work through and can disrupt emotional and relationship dynamics to a huge degree.
When you have these three things all whirling around, people are going to get them mixed up in their minds, and maybe "mis-diagnose" an issue. And you say that there have been other "life" issues that have been a distraction to you, too.
Think about seeing if you can do something to give you some more space to work through one of these issues and put it to bed, before you start working on the others. Only you can say if this is even a possibility, of course - things might already be so entangled that they can't be divided out. This would involve putting one or two aspects of this on hold for a while. maybe stopping the poly and BDSM until you get your health issues sorted (which is the only one that you absolutely can NOT choose to put on hold). This would involved the agreement of everyone involved of course, and may not be possible.
I strongly believe that one of the keys to working through these situations is that everybody involved needs to work as a team with a set of common goals. it doesn't really sound like you have that right now. That way when something comes up which throws you off, rather than people being dismissive, they can help you to work through it.
"Listen, or your tongue will make you deaf." - Native American Proverb