I am scared

I am scared. I was with the man that I love last night and we got into this conversation. At first it was something along the line of fun and we are being honest but then it got serious and emotional. Chris said something along the lines that if we were to have a kid, that he wouldn't run but he would give us a shot and me being the insecure and very non-committal said that I would sabotage it and run. I dont want to have him feel like he is trapped into something that he cant get out of. He is a wonderful 25 year old man that has his whole life in front of him. I sabotaged it right there just by saying that to him right there. He then said that he knows that we are going to be together forever and that we are doomed from the get go. That hurt me. I have been an emotional wreck since then and I dont know what to do with it. Lying in that bed with out him in the morning knowing that i hurt him and realizing that i have become such a flight risk and how much stress that must put on him. I dont want to stress out someone and think that I am going to leave them. I also realized that wow I really love him. 
I am really in love with this man and I am going to everything in my power to not go any where and prove that I am not a flight risk. I dont want Chris to worry if I am going to run away or am I thinking about running away, I simply not going to run away. 
I am scared about if this is going to make him run. We are two people that didnt plan on falling in love with each other and two people that are very much different. I am very planning and up tight, he is very laid back and rather not plan and will tell me no if he doesnt want to do something. I love him for that and I need to become more like that laid back person he is. I admire him so much because he doesnt let anything really gt to him.