Am I Getting Cheated On?

I was on facebook and my boyfriend and I have been going out for almost a week and i forgot to change my relationship status and i decided to change it right now but when set it to in a relationship with Alex ***** It said that he already had a pending relationship request. Also when I looked on his profile it said that he was in a relationship but it didn't say with who. Yesterday his ex posted I love you alex on his wall but he commented and said Cheyenne you gotta stop this I have a girlfriend back off...So what's going on here?