To all of those struggling I echo the earlier sentiments, stick at it!
We got Gizmo at 9 months in 2010. No medical issues, no fear or anything else issues, but I could point blank not get him reliable. (I have owned dogs my whole life an never had a dog that wasn't trained, but then I have never known any animal as stubborn either)
We tried everything except crating (my personal opinion only, I do not use crates) Even when we knew he was desperate to pee, if he didn't want to go outside, he wouldn't. Especially if it was wet, but not always he would stand by the back door shaking, shivering, whining but would not go, and would then pee as soon as we let him in. Other times he would be happy to go out. We have a tree directly across the road from out house and he could sometimes be fooled if we put his lead on and took him to the tree. The scent on the tree would encourage him to go, but again, if he didn't want to go he wouldn't.
He would also pee and poop the second we left the house. I always take them out before leaving the house, sometimes I would be outside for literally a couple of minutes (once I collected a parcel from next door, maybe 1 minute max) and I would get back to a puddle and a poop.
Eventually I resigned myself to the fact that he never would be and kept him in belly bands.
This last 12 months something finally clicked and he will now ask to go out, even if it is wet out. We have not had an accident for about 6 months (with pee, although he will still poop on the puppy pads).
Fidget came to us at the age of 5 in 2012. She is pad trained, but again, sometimes will go if taken outside, sometimes wont and will then come in and pee on the pad. She does have issues however and can't hold it for long. She also submissive, scared and excited pees. She will pee on you if you pick her up! I don't think she will ever be any different. (She has had at least 2 litters of pups, and a spay as soon as she came to us, that may have made a difference)
So anyway... if you got this far....it took 3 years to get Gizmo there! But get there we did.