Don't worry, Kate, most of us find that there are times when it all goes well and times when our running suffers. (Cold and dark are an issue for a lot of us, being human!) The main thing is that you're getting going again!
Take your return slow and steady (run/walk is good, you could look at Jeff Galloway's site for more info and encouragement on that). And since autumn is on the horizon, you might think about whether you can do some things that will make it easier to keep going this winter.
If you prefer running outside (most people do, once they've tried it), do you have the right gear for running in cold weather? Layers are the way to go---there's an article in the RW Beginners section about it, I think. And if you don't like dark, is it possible for you to run sometime during the daylight hours, maybe at lunchtime? If not, don't dismiss the dark. It can be a wonderful time to run! On a crisp evening it can be great to see all the lights in the windows as you go past; and my attitude toward early winter mornings was totally changed when a running friend said how lovely it was to run by moonlight and starlight! And if you really don't like it outside in winter, at least you do have the treadmill.
Look for ways to adapt your running to the conditions that work for you, and you'll be fine! Good luck, let us know how you get on.