You should have booked your medical immediately you got your AIP.
The Doctor there will generate IME for your medical and send to immigration.
Is not too late,just look around and book.Last time I checked,almost all medical locations in the GTA has been booked till August.
Though,I dont know your location,but will advice you book where you can get the nearest date,after booking,call the facility you are awaiting your medical forms.Is also possible you get the medical form before your booking date.
If you are in ontario,you might want to check Ajax.
The link below is for North york and Etobicoke.
https://www.panelphysiciantoronto.ca/
Most times,they dont answer their calls and always booked.