My dog is peeing all over when I am at work, what can I do?

I work about 9 hours a day and come home on my lunch to take the dog out. He is just over a year old and when I am home NEVER goes in the house. I take him out before I leave, on my lunch and when I get home yet everyday I will come home and there is atleast 2–3 pee spots on the floor. This is causing me major stress and not to mention it’s really hard to make sure there is no odor afterwords. Is he doing this because he is mad that I left, or does he just not understand that he needs to wait? Any suggestions?