I've been seeing a guy for 1.5 months. Recently he said that he had hooked up with another girl. Should I continue my relationship with him? We didn't label each other as boyfriend/girlfriend yet.

You know the best for yourself! Your decision about the relationship with him is a derivative of how you feel about him. ask yourself questions like, Is he worth it? Do I want to invest my emotions in this guy? Can I be sure of his loyalty towards me? Is he gonna reciprocate the respect and efforts in our relationship? You will find your answer, your heart will guide you into making the right choice. And if you're still confused, toss a coin, while it will be in the air your heart will be biased towards one outcome, the side of the coin you want to see, there's your answer.

Relationship labels are a huge grey area. It is really up to the couple to discuss and decide for themselves when the relationship has become exclusive and what terms to use. Even the definitions of "girlfriend" and "boyfriend" differ from couple to couple, as does the scope and involvement of the relationship. In many cases for many couples, becoming boyfriend/girlfriend requires a definitive conversation in which both people agree to stop dating others; it is still a good idea to discuss being sexually exclusive in addition to picking out your relationship label. In this case, I suspect that the guy in this scenario was unaware that hooking up with another girl would be a deal breaker. Perhaps he assumed you too were hooking up with other people. If you would prefer exclusivity rather than ending the 1.5-month-old relationship, a conversation saying so would be most appropriate.