I wanted a threesome but now that it’s become a reality I’m getting jealous?

So when me and my boyfriend first met I would say that I wanted to have a threesome. I told him to find someone. But now that he found someone I’m getting jealous. She’s in her early twenties with a nice body. I’m in my late 30s I’ve had kids (we don’t have kids together ) and I need to lose weight. She’s the one who approached my boyfriend and started talking to him. He got really explicit about what he’d do with her. They talk really good and everything. I’ve never talked to her. I feel very jealous and I know that it would change how I feel about him. But I also feel bad because I told him that’s what I wanted. Now I feel awkward He suggested I could watch. Just thinking of it makes me so jealous
I wanted a threesome but now that it’s become a reality I’m getting jealous?
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