I would call labor and delievery and ask (: i was in early labor for 19 hours at home and waited until my contractions were about 5-7 minutes apart but they did always vary in time... some would be like 8 minutes and some would be 3, so I went with the average (i used an awesome app) and sure enough, when I got to labor and delivery I had gone from a 1 to an almost 4 overnight and was admitted and had my son that night (: goodluck mama!
Have a bath and see what happens. Sex can cause contractions but it doesn't necessarily mean they're associated with labour...but sometimes sex can lead to labour.
Could be a sign of labor I would go and get checked if they get really close to each other