Internet friends

I never had many friends irl. But I've always had at least a few friends on the internet whom I could talk to and relate with. There are some who have always been there, ever since I was a young teen. I'm now eighteen. We've shared pictures, talked a lot, played video games together, for years. But as I got older and more difficulties have come my way (and theirs), we haven't talked as much. There is one person among these friends who holds a special place in my heart for helping me through both goods times and bad. But unfortunately, I feel as if we're drifting apart. Every chance I get, I check to see if there's a message from them, but it's become rarer and rarer.
It's starting to genuinely hurt. Although I have more friends I can trust now in real life, I still want to stay in contact with my internet ones. I feel that they're just as important as those I know irl. But I'm starting to feel like that isn't a mutual feeling.
Is it normal that I feel this way? Or am I just being childish?