Ok so i had a three-some with my ex boyfriend and a girl friend of mine. we used condoms, and my ex was way more into me than my friend. basically i'm now a week late and am freaking out. i'm only 18, is it still to early to totally freak or do i need to buy a test? and if i am...pregnant, should i tell the ex or not? + are there any good ways of bringing on a period?