You should sit down and thrash out the terms of your relationship.
Though I will say that my friends who are only swingers often complain that they are straightforward about what they seek in their initial talks and in profiles. Despite this, they often find that seeing the same person regularly can lead to that person thinking their initial limitations have relaxed.
For example, I have a female friend with a male partner who often seek a third male for threesomes. It can be really hard to find a good match so they were happy when they met a man who seemed ideal. They'd hang out a bit as well as the sex and all seemed content.
A few months in, however, he raised the possibility of taking my friend out on a "date" while her husband was away. It was in that moment that she realised it had happened again: the guy had assumed that being happy with the arrangement meant that it could be a progressing relationship. They're just happy with swinging with people who become friends. My friend finds it too awkward to continue after someone suggests something like this.
They don't advertise themselves as poly. They advertise themselves as a couple seeking group sex. That doesn't change with familiarity. They still only want to be friends.
What my friend doesn't mind is clarifying the terms of the relationship and discussion around sti testing and transmission. So she would tell you that you're welcome to see other people because they will be too.
So where did you meet them? What did they initially say they were seeking?
Honestly, break ups happen and it's likely to happen here. Get used to that idea and enjoy what you have while you have it and then move along gracefully, knowing that even emotional pain is temporary and people come into our lives and leave again and that's okay.
People come into our lifes for a reason, a season or very occasionally, a lifetime. You have found the reason - from curious to bi - and you may enjoy a season with them (not literally, like Spring or Summer, but figuratively, like a period of time that will end in due course). You may even stay friends for a lifetime, but most people don't...look at all the wedding photos where ten years later the bride is only in touch with one or two bridesmaids out of half a dozen. People grow, change, move on, and it may well be that you'll be the person who does that. Right now you can't imagine it because you're obviously deeply into them right now, but time tends to the the shine off everything, the rose tinted glasses get put away, and either everyone changes to a new dynamic that doesn't revolve around the bedroom, or they go their separate ways, maybe all broken up, maybe two still together, but rarely three forever.
Hearts hurt when feelings happen, that's part of the experience of being human.
yes I have had this happen before with someone who I honestly thought was going to be in my life forever n it hurt an hurts so bad that I know even though this to might or will end it will hurt an I honestly don’t think my heart can handle a hurt that I may not be ready for u know how they say u always remember your first everything first kiss first time first heart ache idk how to prepare for a first heart ache of not loosing one but two ppl who were your first huge out of comfort experience lol first girl kiss first three some first i don’t even know what to call it after the man who you thought was your soulmate left you an if I’m honest have not forgotten n miss horrible idk a part of me wants to cut n run n just never get close to anyone else n part of me feels guilty for talking to other couples I know I said I wanted the relationship with out the relationship all the fun n none of the drama know my heart is not letting me be cold like I thought I was