Help!

Okay guys, about six days ago my boyfriend and I were doing things and he ended up going inside of me with no condom on. It was only about 30 seconds, a minute at the most and we stopped because we didn't want to go longer without protection. The next day (Sunday), my stomach started feeling funny and has continued to feel that way (it's now Thursday) I also have mild back pain and defecate a little more than usual. Do you think this could be pregnancy, or something else?