If it is any consolation, my experience is also similar. After the catheter came out my bladder was clearly holding a small amount successfully, but beyond that it leaked constantly without me feeling any warning. Very slowly over the following months the number of pads I needed per day reduced as the capacity grew any my awareness of fullness improved. (Night time was much better, it only took a couple of weeks before I stopped leaking, becoming aware of the need to get up and wee reasonably reliably).
As I have commented here before, for me the psychological breakthrough was when I stopped needing more than 2 pads a day and could confidently do anything I wanted just taking a spare in my back pocket. That took me about six months though, and now at over a year I only need one pad which sometimes hardly gets wet (unfortunately the need is difficult to predict). I am told that most men get control somewhat quicker.
The pattern was just as Nomad describes, which makes sense from the anatomy and physiology textbook explanations. The bladder is something like a balloon, which you can blow a certain amount of air into before the rubber starts stretching after which it exerts a back pressure from the rubber elasticity. The average bladder holds about 150 ml without stretch, after which there is extra pressure from its expansion which requires a stronger sphincter. The nerves actually do signal to the brain that the stretch is occurring but right from the point of potty training as an infant we have learnt to ignore the signal until a considerably greater volume is reached. I remember pub sessions when younger needing the toilet roughly as often as the rounds were bought, in other words implying a capacity of 500-600 ml.
In my case I had poor urinary flow before the operation due to prostate enlargement (assumed initially to be benign and helped with the drug tamsulosin). That means my bladder never emptied fully so I was using it all the time at levels of stretch which I had learned to completely ignore initially. That may have explained why I so readily leaked without warning. Since then my awareness of the need to go to the toilet at lowish volumes has improved while at the same time the stretch my sphincter will work against has become better - just as Nomad describes. I find that what I am doing is a factor, if I am mainly sedentary I easily notice my expanded bladder, whereas when I am doing something moderately active (even as trivial as walking round the shops) the awareness is reduced and possibly the movement also works the sphincter harder so it starts to leak sooner.
So hold on in there Pugs, the leakage is a real frustration at your stage but little by little it will improve!