Marriage Bed Confession

I met my fiancée five years ago when I was fresh out of medical school. She was a few years older than me but we hit it off right away. We started dating, then moved in together, and after about two years she popped the question. I said yes without hesitation. Now here we are, engaged for almost three years. Planning the wedding has been stressful but exciting. We're both 30 now, so marriage seems like a natural next step. It's just... there's something off lately. She still tells me how much she loves me all the time, and I love her too, but it feels different. Last night we went to bed as usual. As soon as the lights were out, she started talking about all this wedding stuff again. And that made me think of what my mom always said, you shouldn't talk about stressful things in the bedroom, save the bed for love and intimacy only. So I told her I wanted us to make tonight just about being intimate. She seemed surprised but agreed. We got into a playful mood, undressed each other slowly, made out, touched... Then she said something that stopped me cold: 'Are you sure you're ready? Because sometimes when we do this stuff it feels like there's an expiration date on our intimacy and you'll be busy planning the wedding soon.' That threw a wrench into things. My fiancée's always been straightforward, but hearing her talk about feeling rushed made me feel terrible. We stopped, I tried to reassure her, promised we'd take our time in getting married. But that wasn't quite what she was saying either. I know deep down I'm not ready yet for the long-term commitment of marriage. It's just... I've never had a serious relationship before and this one is so much, so fast. So instead of being honest with her about my fears, I stalled, I kept talking in circles until she fell asleep. Now here it is morning and my heart feels heavy. Maybe I shouldn't keep pushing things forward when we're not actually on the same page.