Braxton hicks can happen after intercourse. Usually comes and goes just a few seconds and yes will go away when you change your position. Contractions is a very heavy feeling on your vagina and you'll also feel pain from your back to your abdomen. You'll feel like you badly want to poop. The pain will not go away no matter how you change your position and it comes in intervals like 2 mins apart or even so. Your waterbag might break first before the contractions come or your mucus plug might come first before the contractions or just the contractions only. Don't forget to count the pain intervals. Head to the hospital if it's between 5-10 mins.