My pit/jack russell mix is driving me crazy...help?

Okay, So i got my puppy at 5 months old, he is not 6 months and technically ive only had him for about 3 weeks now. He was good the first week, and now he is becoming a bit much to handle…I run home on my lunches at work to take him out and as soon as i get home take him out for the bathroom as well. I also take him before i go to work, and of course while i am at home at night I take him out often. He will go to the bathroom outside almost everytime i take him out, yet STILL he will pee and poop in the house. I laid down puppy pads and for awhile he would go on them, however he seems to be getting worse, by not using the pads and just going whenever he feels like it. I yell at him and tell him no then take him out right away, then clean the mess. He is a smart dog, learned sit lay and paw all in one day pretty much and I know he understands me but i feel like he is acting out for some reason. I recently started taking him for long 45 min walks to get rid of some of the excess energy, and when i can i bring him around my friends dogs and to a ball field to run. He usually stays by my side at the field, and generally he is a good dog minus the accidents in the house and some nibbling which im guessing is just puppy play and i usually walk away from him when he starts. Can anyone help solve this problem, it is very very stressful on me and I don’t know what to do. My job just relocated as well and I can’t really make it home on lunch to take him out anymore, I got a speeding ticket trying to make it home today. ....im going crazy….