hhello i have a girlfriend and we have problem.

lately this month we are upto having sex but i am on boxer and she is on her underwear, no flesh to flesh happened , just on our wears ,she is not having spottting yet, she is 9 days delayed, we tried to use hcg Pregnancy test and showed up Negative. she is also stress with our projects. is there a chance that she is pregnant? or is this something to do with stress? we have so much probljems at school though. please help us