Mujimuji,
I also had back pain this cycle when I injected the ovulation medicine. The back pain suddenly disappeared when I ovulated.
Yorn,
Most doctors will monitor the egg size until day 17-18. The egg size should be about 18-20 before they give you the HCG to stimulate the ovulation. If the eggs remain small, you need to wait for another cycle or the doctor will increase the dose of the medicine.