Making a Mess. in MY NEW PUPPY ~

My goodness. I must upload my recent pictures of Baby this weekend so I can show what a real Stinker she has been this week. One day while I was gone she got into a small trash can & found some Kleenex. She made confetti decorations all over the living room!! The thing is, she seemed so excited about her "mess" when I got home. I'm having a really hard time getting her potty trained. She knows what going outside means, & she knows she gets a treat when she pottys outside, but.... if I don't take her out all the time, she will pee/poor where ever she happens to be :( She is 3 1/2 months old, so we have been working on this for about 2 mos. You would think she would have it down by now. Any suggestions?