Hi
I'm Dr Prashant Parate. I'm Specialist of Shoulder and Knee. I treat patients with similar complaints regularly. From complaints you have described, apparently you have injury to knee ligaments as well as meniscus. X ray doesn't show anything in such cases. MRI is most important investigation after clinical examination and x Rays.
MRI should be done at best centre with 3 Tesla machine so that all details can be seen on MRI. 1.5 Tesla MRI is also available, but 3 Tesla is better. Compare 30 megapixel with 15 megapixel. Similar differences are present in 3 Tesla and 1.5 Tesla machine.
Your treatment will depend upon findings of MRI which may vary from some exercises to surgery. It's been 4 months now and medicines have no role for treatment.
Next Steps
MRI has to be done. It's your knee which is damaged. MRI will be expensive, further treatment will also be expensive. If you delay proper treatment, there are high chances of developing arthritis of knee at young age. Then you will need knee replacement.
It's better to get MRI and check status of meniscus and ligaments.