mine were really mild and about 12-15 minutes apart on average (although some might of been closer to 15-20). they were like a braxton hicks but with slight period like cramp and had a start, peak and finish (even when really mild...you could visualise it "rolling" towards you ITMS).

they never got regular, sometimes they went to 2-3 minutes apart but never lasted longer than 30 seconds and then would go back to 12-15 minutes (at some points i wasnt even sure that they were happening anymore lol). then about 3 minutes before my waters broke i got 2 in a row and then POP! after that i would get a bigger contraction every 10-15 minutes that would last 60-90seconds and required concentration and my calm breathing exercises: an hour later of that kind of thing she was born

HTH!