Why do I get anxious when my boyfriend goes out drinking?

Perhaps you'd be afraid of what he may do under the influence, or what could happen to him. There are many reasons to feel anxious --fear of cheating, fear of a car accident, etc. Whatever it may be, you are entitled to your own emotions. It is also normal to feel worried for a significant other and if this a something that makes you feel uncomfortable, maybe you can consider discussing this with your boyfriend when you feel that you should talk about it. Or imagine what you would do for a friend who is going through this.