Answer: Based on your description I am not certain why the branches are breaking. The plant should be self supporting. One possibility might be an oversupply of nitrogen could force it into abnormally fast and weak growth with an excess of large foliage, or possibly heavy rains and wind could cause breakage. Another possibility is an animal (or children) running beneath it and physically breaking the branches. With a little detective work perhaps you can determine the cause.
You can prune broken branches off, cut just outside a side branch or trim it neatly just past the trunk. (Do not leave a stub but do not cut it quite flush, leave the swelling at the base of the branch intact to promote fast healing.) You could also try to thin it if it seems excess weight is causing the problem. You could still trim it back now, but I would not trim again this season as the new growth will not have enough time to harden before winter. The rule of thumb with this shrub is that most people want to keep it relatively small, so they cut it back very hard in late winter to early spring routinely every year. You would also need to prune out any winter damaged or winter killed stems each spring.
I hope this helps.
Q&A Library Searching Tips