Do It Yourself

I've recently installed new brake pads on my bike, all good. They are disc brakes. After a week they were too loose, thought it was because they were new, so readjusted them. A week later and I have to readjust them again. I only cycle about 70km per week. Before the pad replacement I didn't have to do it so often.

Is it still because they're new or am I forgetting something? Thanks.