Hiv is very difficult for a man to contract compared to a woman. This is science talking! I believe that the exchange and contact was not "insertive" vaginal intercourse.
I can assure you that the probability of contracting hiv is compared to a snowstorm in miami!
You do need to watch your behavior! If you are concerned, take an elisa and have protected sex until your window period is complete (from date of last exposure). However, you should expect a neg result. Honestly, I really don't feel that you have a window, if what actually happened was exactly as you have written. You have a more likely chance of contracting other std's.
What do you think, should be the question! You sound mature enough to understand what you're dealing with and seem to know the best answer. If you are concerned, it may be driven by guilt. Work on it! If you have sex with anyone else other than your girlfriend, you must make sure it's protected and have to take the responsibility of accepting the consequences.