Help: I can run a mile now but after that I can't go any further. How do I steadily progress?

I'm doing pretty damn good. A month ago I couldn't even run a minute and now I'm up to running a whole mile(barely right now, I just reached the mile yesterday.) but after that I can't do anymore. So how do I add onto it next to keep a strong progression without overdoing it. I was hoping to get up to 2 miles by the end of April and then start working on speed.