Possibly pregnant?

My boyfriend just left for the Army yesterday. 2 days prior was our anniversary. We were in the mood and out of condoms.. we went for it anyway. Haven't taken a test to get the positive/negative yet but if its positive it'll be my first child. My period ended about 3 days before our anniversary. Im feeling a little bit of pain downstairs but i feel like it is either stress or just my anxiety. Any tips if its happening for a new possible mom? Any ideas how to break the news to him? (Hes gone till September)