What you have described has all the hallmarks of a ruptured anterior Wikipedia reference-linkcruciate ligament. This would be the thing i would look to rule out first and foremost. Get some treatment and get on the list to see an orthopedic specialist who can properly diagnose your condition.

A physio who has experience in sports injuries and dealing with this type of injury should be able to diagnose you and manage your condition approprately. See if you can seek out a good sports physio while you wait for an orthopedic specialist appointment. Meanwhile google ACL rupture and see if you think your symptoms are similar.

Good luck