It is challenging to determine the exact reason for your boyfriend's behavior without more context and information about your relationship dynamics. However, there are a few possibilities that could explain his sudden change in demeanor:
Jealousy: Your boyfriend may have felt jealous or threatened when you mentioned another guy you were talking to. This jealousy could have caused him to feel bothered or uncomfortable, leading him to ask for space to process his emotions before discussing it further.
Insecurity: If your boyfriend has insecurities about himself or the relationship, hearing about another guy may have triggered those feelings. He might need time to process his emotions and understand why he reacted the way he did.
Miscommunication: Sometimes, misunderstandings can occur in relationships, and what might have been a casual conversation for you could have been perceived differently by your boyfriend. He may have misunderstood your intentions or the nature of your interaction with the other guy.
Past experiences: Past experiences of betrayal or infidelity, either from this relationship or previous ones, could be influencing his reaction. These past traumas might have made him more sensitive to certain topics.
Relationship concerns: It's possible that his change in behavior could be related to underlying relationship issues that were present before the conversation about the other guy came up.
Emotional overload: Your boyfriend may have been experiencing a surge of emotions that he wasn't prepared to handle at that moment, leading him to ask for some time to collect his thoughts.
Whatever the reason, it is essential to approach the situation with empathy and understanding. Give him the space he asked for and, when you talk later, try to have an open and non-confrontational conversation about both of your feelings and concerns. Communication is key in resolving issues in a relationship, so be prepared to listen to each other's perspectives and work together to find a resolution.