Dog Pees Inside When Home Alone and At Night?

I have an almost 8 year old Malkie (Maltese and Silky Terrier), he is wee wee pad trained as well as trained to go outside. Whenever someone is home he will always go on the wee wee pad, even if there is one spot where he already went, but generally we try to change the pad right after. He has always been left alone when we are at work so I know it's not separation anxiety. We had his kidneys checked and everything else and he is a healthy dog. We also tried to crate train him as a puppy and even recently and he hates it, he scratches at the crate and his paws start to bleed so we stopped putting him in the crate. But every time he is alone or after we go to sleep we either come home or wake up to pee all over the kitchen and some random parts of the house. The wee wee pad will be clean, but there is pee somewhere. I moved out a few years ago and left him with my mom and it hasn't gotten better or worse he is still doing this. He's gonna be with me for an entire month and I don't want my apartment to have pee all over it. I know you have to catch him in the act to discipline and it's pointless to do it after the fact so I have no idea what to do to stop this behavior. Please help! Thanks!