When a boy says "You are so beautiful" or "You are pretty" to another girl and doesn't talk about the person he is currently with (you) at all, it could be interpreted in different ways depending on the context and the individual's intentions. Here are some possible explanations:
Complimenting someone else: He might genuinely be complimenting the other girl without any romantic intentions. People can compliment others on their looks without it implying anything beyond that.
Casual comment: It might be a casual comment with no hidden meaning. Some people are simply comfortable expressing admiration for others' looks without any ulterior motives.
Trying to make you jealous: It's possible that he is saying this to provoke a reaction from you or to make you feel jealous. This behavior can be immature and may not be a healthy way of dealing with emotions.
Loss of interest: If he used to compliment you in the past but has stopped doing so, it could indicate a loss of interest or a change in feelings.
Lack of awareness: He might not realize that his comments could be hurtful or insensitive, and he may not understand the impact it has on you.
In any case, it's essential to communicate openly and honestly with your partner about your feelings. If his comments make you uncomfortable or you're unsure about his intentions, it's okay to talk to him about it and seek clarification. Healthy communication is vital in any relationship, and discussing your concerns can help both of you understand each other better. Remember, everyone's perspective and intentions can differ, so having an honest conversation can bring clarity to the situation.