Am I overreacting to the whole situation?

So my boyfriend and I have been together 1 year 6 months officially but known each other for 3 because of work, he's met my mom's side of the family and my friends and he's suppose to meet my dad this weekend. Things are going great except he calls my idea of a relationship unrealistic. This is my first relationship ever since I had to have therapy after I got SAed 5 years ago so I started avoiding men afterwards but I got out of my shell and decided to give him a chance, other guys have asked me out and I have rejected just for him.

So he's into certain things I'm not like oral but he's only done it to me once I haven't been doing it the past month or 2 since we got together its not something I enjoy and I just didn't think I should do it anymore. He recently came to me saying he wants an open relationship since I won't do that and that's not the only reason he wants to also wants to get another girl involved in the bedroom, I told him he can sleep with other people if he's ready for the consequences. He keeps saying if I wanna experiment with someone else I can and we can talk about it but I'm not interested in those kind of things, he thinks monogamy is unrealistic. I just dont know where all this is coming from when we were clear from the beginning what we both wanted but my needs weren't considered for this duration. He proposed 3 weeks ago on our trip, it was great. The 3 of us, his kid , him and I were out of the country I'm south america a trip I planned for months and we finished our hike and he did it when we got to the top of the hill. It was cute his kid got on one knee as well. I'm starting regret the whole thing and I'm thinking of breaking things off before the weekend with my dad. I've expressed my dislike to his idea and I think if this is what its gonna be like I should leave. He complains that I hold back and I have no reason to be nervous when we're intimate, i just can't help it, it still all feels new to me.

Am I overreacting to the whole situation?
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