my (22f) boyfriend (23m) said that his favourite position is one we can’t do. should i be offended?

My boyfriend and I had finished having sex when during pillow talk I asked what his favourite position was. I had expected him to say one that we had done together because after I asked he smiled to himself and in my head I thought he was probably thinking about us doing it, which obviously made me smile too. But then he said that it was a position in which the girl wraps her legs around him and he stands up. For context I am a slightly bigger girl, not too overweight but I’m tall and a little chubby. He is a little bit taller than me but very strong while being quite skinny and muscular. We have never done this position, which just made me feel very strange and somehow sad. He then said that he doesn’t think we’d be able to do it, which made me feel even worse. Him and I haven’t been together for very long, but throughout our time together he mentions his ex a lot. They had been together for a very long time before they’d split, and they’ve been split for about 4/5 months. His answer just made me think he’s thinking of her and what they’d done together, again. The theme of me being a bigger girl has also come up before, and I already feel too big for him. Am I overreacting? Should I talk to him about it? I kind of just cut off after he said it and haven’t said much. Please tell me if I’m being crazy lol.