Is it normal to get sad when...

Is it normal for me to become saddened when I see that my group of friends are messaging each other all the time except for me. They might message me once in a blue moon, but it still hurts a bit. I'd message them, but when I type a dickload of text to someone, I always get that annoying as hell response that barely says much. For example: "Yeah, I miss you too." The end. Also, when I say bye to someone I normally chat with, in real life or online, and they don't say bye like they normally do, like for example leaving a heart at the end of a message, it gets me down. Don't get me wrong, I'm generally a happy person, but some of these stupid things get me down. Is it normal?