It is possible you pruned your mock orange at the wrong time; it should have been pruned after it flowered, and the new growth
made in the summer would flower in the following year.
If you pruned it late in the year you will have cut out most of next years flowering stems.
Alternatively you may be feeding it wrongly, e.g. giving it too much nitrogen, hence the mass of growth.
Commence feeding the shrub with sulphate of potash and this will encourage more sturdy growth.