Threesome

Hello ladies, I feel like I can’t talk to anyone but you about it but my boyfriend of three years asked me to have a threesome... let’s take it back to when we were talking and getting to know each he said if I was down to have a threesome I said yes, but it never happened. Now three years later aka a few days ago we were all sorts of kinky and I asked what other fantasy he had he said he has been wanting to do a threesome with me and another girl. See me with a girl and have me do her with a strap on and vise versa... we had a lot of back and forth. I ended up saying with A LOT OF RULES AND REGULATIONS. I never gave him the option of a guy because it’s not my thing. I’m just worried that everything goes to shit since he did ask my parents for my hand in marriage and have spoke about having a family. I’m also very possessive about him, you mess with him that’s like messing with me. I don’t know ladies, give me some opinions. 😩🙃