BH start as early as 8 weeks, from the reading I've done. Most people just dont notice them very early. I've had them from the beginning, and remember having them quite early on with both my others too (I dont think I noticed them/had them as often with #1 but its been more each time).
I find they often mean I need to relieve my bladder, and sometimes its just from pushing and poking.
I'm jumping in from October DDC to offer you some piece of mind. I started getting the tightening aka Braxton Hicks around 14 weeks. They are totally normal and I now say "I'm practicing" instead of "I'm getting a BH or contraction." Somtetimes I get up to 5 in an hour but then they go away for an hour or two. If I have to pee I get more. They should not get painful or increase in intensity or get regular (every 5 minutes or so). Figure out what is "normal" for you and they should just stay that way. Now that the baby is moving a lot I get more as I get kicked. My MW said that I should try to ignore them (practice for early labor) but still notice if they are getting stronger or regular. Easier said than done.
I've been getting them for several weeks now. I don't remember getting them this early with my DD, but I do remember later on maybe 20 weeks (?) how hard and round my belly would get. It was kinda funny looking! With this pregnancy it isn't so obvious but I can definitly feel it!
I've been noticing contractions here and there for weeks. I never feel anything uncomfortable, only notice the firmness, tightening in my squishy belly, lol. It was a long time into my first pregnancy I think before I noticed them for what they were. I've noticed them early on this time around, and I enjoy it - makes me notice the baby part of being pregnant rather than just the feeling-crappy part, LOL. Feels pretty good to me, really, kinda like giving the baby a hug. (or is that just because of the timing of when I have the most of them?)