Bf is on tinder

Hi everyone, my boyfriend and I will be together coming on 4 years. I’m 25 and he’s 29. Today, my cousin called me to let me know she saw his profile on tinder last Wednesday. We discovered that it is in fact his account and that nobody made it for him. He’s currently out of town and I’m supposed to be picking him up from the airport tomorrow. I’m not sure how to go about addressing this. I’m truly at a loss for words. All week he’s been talking about marriage and proposals. Do you guys have any advice for me? I feel so heartbroken.