Your technique for getting on the bike and taking off sounds quite risky, for someone who has recently had pelvic fractures especially. I've never done as you described (moving off before swinging the leg over the bike) in decades of riding. Is your seat too high? Does your bike have an unusually high bottom bracket? Maybe you need a different style of bike, such as a crank forward design, where you can easily reach the ground with your feet while seated. Can you try lowering your seat, as a temporary measure?