Why am I not sore or tired after running?

I've been running 4-6 miles everyday for the past week, about 50 minutes altogether. I'm not sore, or even tired. I've been thinking maybe I need to run faster, since I do sweat a little but not a lot and my heart rate isn't THAT fast. Maybe I just have good endurance, I really don't know. The weird thing is, I did cross country for four years, but I had to take a year off so I haven't ran in a year, then I started on Monday and I can magically run 5 miles and not be sore? I also lifted everyday from September to June, maybe that's why. I just don't know lol.