Is my ankle sprain ready for rehab?

About 5 weeks ago, I sprained my ankle (2nd degree) and had a very small fracture. I wore a boot and did the elevating thing with ice for a while too. The doctor told me I could start putting weight on my ankle with the boot and start doing exercises to get the flexibility and strength back. My ankle is very stiff still. I can bend my ankle slightly up and down, and move my toes a lot, but whenever I try to move it as much as my other ankle, it just starts to feel like it is too stiff and I"m going to pull something. I'm only supposed to be doing exercise that involve vertical rotation, nothing from side to side yet, but I'm scared because it feels like if I move it too much up or down it is going to get messed up again somehow. I can put a decent amount of my body weight on my ankle with the boot and it doesn't hurt anymore. Still some slight pain when I put too much weight though. What should I do? Is my ankle too stiff from the lack of movement...is it normal that it feels like it does? Should I do therapy?