Maybe you gained muscles? I gained weight when I first started, perhaps because those muscles were all but inexistant???
Don't watch weight too much when you first start. Focus on how it makes you feel, and how much easier it is. That worked better for me, as it was easier to get encouraged about what I did. The scale-watching put me down a lot @ first.
The 8 miles you do @ night is okay. If you do a one way 30 minutes commute 5 times a week, I think you should get benefits out of it. though if you can, 2 sets of 8 miles will def be better for you.