When did you go into labor w/ your first?

I am 37 weeks pregnant with my first and I just feel like I'm going to have him earlier than my due date, which is Oct. 26. I don't know why I feel this way... I haven't dropped yet or anything. I just have a feeling, like when I had a feeling it was a boy and it was. When did you go into labor with your first and were there signs leading uo to it, or did it just happen? The only sign I;ve had so far is period like cramps.