Kobe did the same exact thing until he was about 8 mos old. since we lived in an apartment, I had the pads in the laundry room. when he got l little older (7 mos), I decided to start walking him when I got home from work. I would walk for about 30 minutes and he never did anything. I did the same thing for 2 weeks and one day he lifted his leg and peed. OMG I went crazy and praised him and called everyone to let them know that kobe went outside. But he still hadn't pooped.
Then about another week went by and he pooped. Then after that, he refused to use pads. Now, we live in a house and he is totally trained and goes outside. Just be persistant and praise and treats.