I told my parents that I'm in a throuple

For context: me (18 F) and my boyfriend (18 M) have been dating for nearly 3 years. After maybe a year and a half-ish I started realizing that we were getting serious and with the way we are with each other, we may last well past high school. I'm bisexual and most of my relationships with women prior to meeting my boyfriend were probably the worst it could get. I would become deeply infatuated with people who were so far gone in their mental health its not even funny, and most of these relationships were devoid of physical affection (not even the basics like holding hands, hugging, kissing, etc). I had always wondered what it would be like if I could be in a relationship with a woman where I wasn't miserable 😅 and so I brought it up with my boyfriend. He was pretty supportive of it and also explained that I was the only person he had intercourse with and it was something he was curious about. The first relationship was a dumpster fire and he ended up getting deeply attached to this girl even though she had mostly ignored me. But despite basically being in love with her he told me he'd be with me forever and I saw that no matter what happened he would be there with me through every step of the way, and pretty much all jealousy faded at that point. We've talked to girls together for as long as 6 months, and I slowly realized i was on the ace spectrum somewhere, most likely demisexual, and having no strings attached or FWB was really really hard for me, and we started pursuing real romantic relationships. Most of these relationships me and him did well but the person in the relationship was very toxic. For instance, one of the people we dated claimed near the end of the relationship that we had never seen her sober once before in their presence, and she had to constantly be drunk in order to see us. There were some issues with communication as well.

Now, I think we have finally locked in on someone who is quite literally perfect for us. She's committed, and fiercely loyal, she's silly in the most awkward but also cute way possible, and while I tend to initiate things in the bedroom, she babies me and comforts me outside of those sorts of things. And she actually communicates openly about her issues and what she is and isn't okay with. I can't speak for my boyfriends experience with her, only to say that he has expressed how much he likes her and it's clear he cares about her opinion and genuinely does see a future with her. We have all been intimate with one another and it hasn't been a cause for jealousy. We adore seeing each other together on private dates, and we get along on group dates as well.

Because I am really feeling like this is going to work out, I made the decision to let my parents know, because pretty much everyone else but my extended family already knows, and everyone else's parents know as well. But it was a wreck, and they kept really emphasizing on the fact that there's going to be some sort of crazy misunderstanding and everything is going to fall apart. Or, what if she gets pregnant? Will my boyfriend marry her instead of me?? And they are completely and utterly convinced that I must have a favorite or I must feel unfulfilled in my relationship with my boyfriend.... And the truth is, I do favor my boyfriend with certain things, but not because he's "better", just because he's been there since the beginning. However it's not like it's obvious, or anyone gets left out. I still give her an equal amount of affection, I'm not jealous when he's around her, and not only that, she RESPECTS that me and him came first. Not only that she's had a pretty intense crush on us from the beginning about a year and a half ago, we just didn't pursue it because she lived over 2 hours away at the time and we were just starting our journey being poly. My parents just seem to see it from a monogamous perspective, and they think that if I'm in a throuple, it's an open door to go be with other people as well, even though that's really not the idea at all. They also seem to think that if my boyfriend kissed a girl I didn't know, and that I wasn't involved with, that I can't be mad because I'm supposedly poly, even though me and my boyfriend agreed that's cheating in our book.

Sorry for such a long post, hope you stayed until the end there. I'm just looking for some encouragement because I'm getting in my own head about the whole situation and I have a tendency to panic and ghost when this sort of shit happens ✌️I really want to make this work but all I keep seeing is sad stories and breakups...

DISCLAIMER: I'M NOT UNICORN HUNTING!! The last thread I posted this on really dissed me and called a closed triad like this unicorn hunting. I do mention that I would most likely stay with my boyfriend after a breakup not because he is necessarily the "better" partner, but simply because my girlfriend does not want one of us without the other. The feelings are mutual and this is a non harmful, consensual agreement that I had with both partners.