I feel like I'm losing my best friend. He suddenly has a girlfriend at school. When he was single, we used to be super close and he was so sweet. We used to eat lunch together, do homework together, etc. Now, things have really changed. It seems like he forgot that he once had a best friend. He's always with his girlfriend (and that's reasonable because they're in a relationship) but, somehow I get jealous. How can I let my best friend know that he's leaving me behind?