Threesome?

Jensen • 18 & Early Childhood Education major
My boyfriend is currently wanting to do a FFM threesome and I'm on edge about it. I've NEVER done anything like that so can someone tell me stories? Or their experience? I just feel like I'll get entirely too jealous. We always play around with Dom/Sub stuff and humiliation but I'm scared I'll get jealous or won't be able to enjoy anything. Please help!!  Thank you in advance!💕