I injected ovidrel two days ago when my follicle was 21mm. when i am about to ovulate or have i already ovulated? how ill know

Ovulation ?: Ovidrel will generally cause ovulation, but the only proof will be pregnancy, since the "ovulation kit" if used will not be accurate b/c of the Ovidrel injection. If the follicle which was "21 mm." was the follicle which ovulated, another ultrasound will show this to be absent. Another way would be if your period starts in about 14 days after your Ovidrel (i.e., pregnancy did not intervene).