My dad taught me how to ride a bike, which still amazes me as I am somewhat uncoordinated.
First he took me to the top of a low grassy hill. I just stuck my legs out to the side and rolled down to get the feel of keeping the bike balanced, which was a new thing after the training wheels.
I did that for a while, and when I had it down I practiced on flat ground. I would push off and my dad would count the number of times I pedaled before I had to put my legs down to keep from falling. Each time I would try and beat my previous record until eventually it was easy.
I hope that helps, and good luck. I know it can be frustrating.