Lexis started to feel something in his chest whenever he saw you. His heart would pound against his ribcages. It only happened for you.
That has happened to two girls in his lifetime and it didn't end well. He tried to throw away his feelings. Lexis didn't want to feel something like that towards you, in fear his heart might end up like it had before – broken.
He distanced himself away from you. You couldn't place your finger on why that was happening. You thought it was something you had done, and was getting scared that he might just cut all ties with you.
He even stopped sitting next to you in Biology again.