Definitely looks like a rock to me! Even though sculpt and flow is really important for a rock, remember that textures and materials will play a way bigger role in the final feel of a rock than the actual geometry.
Thanks for your encouragement guys. I made substance which I made for asteroid which looks decent. I think I will modify this. This asteroid is actually based on procedural node generator I made in Lightwave.I also think about making rock generator for infinite rocks. .
Looks like a rock to me too - a pretty good rock. :) Is there a specific style or reference you're going for? Perfectly normal to doubt your own work too, I often look at my own stuff and ask "would other people know what it is?"; answer is usually yes and I'm just being overly critical/sceptical :P
That's where you went wrong. Your rocks look pretty decent, and I don't think anyone would question them if they were thrown into a scene, but if you want to push the realism you need to take the time to carefully look at reference.