It sounds like you are playing with bias edges too much. Best to try not to cut too many bias edges which are joined to other biases. Don't iron and press all of the time if you notice your quilt is growing. Just gently finger press. If it becomes a real problem, you might find that doing some 'stay stitching' around each shape might be the best solution. It will be tedious but is an age old dressmaking trick for bias edges. Hope you have better success with it.