What variety are you growing as there are summer cropping sprouting broccoli?. If this is what you have they have formed the broccoli spears as they are bred to do and then gone on to flower.
If you want sprouting broccoli at the most useful time in early/mid spring you need to grow the right ones - simply called "sprouting broccoli" in the catalogues or there are one or two hybrid ones that are not a huge improvement in my view.
These overwintering types are tough. I have seen unprotected plants holed by caterpillars, then shredded by pigeons and still go on to produce copious amounts of spring broccoli.
So there is no harm now in cutting yours right back and harvest any new broccoli spears that form. You have nothing to lose after all. And please don't let this experience deter you from persevering with this crop since the overwintering type is one of the easiest, most resilient and tasty crops you can grow.