I had to do them, plus wear the TED stockings for the same four weeks. The jabs aren't too bad, once you get used to them. At least the needle should be sharp, being a use-once item.
My daughter had to do them after her Caesarian, a few years back. They're very commonplace nowadays, and a good thing too. My memories of patients back in the 70s with DVTs and pulmonary emboli (and all too often involving the undertaker) make me 100% in favour of post-op anticoagulation.