I've joined the Military, but realized that I don't want to go. I can't just walk away because...?

My recruiter talked a good talk. I was settled on the Marines but now I'm second guessing myself, because I went to the Army branch and they had a lot of good stuff to say too. But when I think about going to MEPS, I want to throw up. When I think about boot camp, I want to throw up. When I think about the Marines, I want to throw up. Maybe this is all because my recruiter has pressured me into going to MEPS. I have signed some papers with him, and he has my information. He has paid for a hotel for me and we are scheduled to leave on Monday. I told him I didn't want to go, but he keeps insisting. I don't want to go. My heart is not in it. It just isn't. My friend and I were planning on doing the buddy system, and now we might not be able to do that. I don't know what to do. I just wanted more time to think about it but he won't give it to me. What should I do? I'm scared, uncomfortable, angry, and disgusted all at the same time with the situation...