Welcome to LD4all, Imagination 
Well, what you’re decribing sounds like extremely low lucidity. Once you have the “I’m dreaming” moment it’s incredibly important that you immediately stabalize the dream (by rubbing your hands, touching the envrionment, etc.) and find something to do. I suggest you come up with a list of things to do so that when you are lucid you never have to think “what now?”
It all boils down to confidence and calmness. If you start to worry about the dream ending, it will end. If you worry about having nothing to do, you will have nothing to do.
There are some great resources in the Knowledge Base that you might want to check out. One in particular is the Prolonging Lucid Dreams topic by Sandra.
You may also want to check out this lovely Motivation Topic by Lord Antares.