Well I can tell you this, the first time I did it with this guy, I was the same way. But as soon as I got my mind off of things, my period came. I kind've found things to worry about instead of my period. I know its scary trust me... I was so paranoid, but I took my mind off of it and my period came.
Don't worry your probably not pregnant, it's probably just stress :d
also, if he didn't come, maybe thats another plus for you, but I cant be sure...