Thank you very much for your answer! My boyfriend actually told me the same thing, that the fear would probably be worse than reality. If that's true, it would probably be the best to start right away. But I'm not sure if I'm ready:S
The past few months we have been practicing with just kissing other people at parties from time to time, but my demand always was to do it together and have some kind of threesome. But lately I've been realizing this isn't easy for me either. Being intimate with two people at the same time stresses me out too much, but the idea of my boyfriend being alone with another lover scares me even more.
The reason why I thought it might be easier for me to start dating first is because I really want to find out if I can love more than one person at the same time. When the answer is yes, I would know poly could have advantages for me as well. For me it's harder to understand the needs of my partner when I'm not experiencing them as well.
Lucky for me my boyfriend is patient, as long as I'm making progress. And yes, I think we should talk a lot more about this subject.