I totally get this. For as long as I can remember, I've kept my art a secret from the world. I haven't posted my own art for 7 years, and now that I look back, I kinda feel bad about it. The reason why I haven't posted is for the same reason: "I feel that I'm not good enough."
The problem is, we'll never feel we're good enough. Ever. That's kind of the whole point of development. The moment you feel that your art is perfect is the moment you stop developing and learning. Don't worry if your comic's good or not, because you'll be able to develop over time.