I'm in a pickle, please help!!!

I sprained my left knee in May after a fall in gym. I was taken to the hospital where I was told that I had sprained it, and there was a high probability that the ligament had stretched to the point where it snapped. I was given crutches and told to use them for three weeks and get my checked out at the end of the three weeks to asses what should be done. I was also told that because of the severity of the sprain, I was likely to need physical therepy. However, I was unable to make the follow up appointment and I couldn’t get another one scheduled because of the cost(my mom had to pay for the first one we couldn’t make.) I still have pain in my knee and I have trouble walking properly. It’s extremely painful to bear a lot of weight on that leg or bend it too much. I cannot squat, or bend it more than 90 degrees. I have to walk on the ball of my foot with my knee straight. I only do this on the left side. I also cannot walk fast or for long periods of time. I’m not sure what to do. Should I beg my mom to make another appointment when I know it will be difficult to pay for? Do I do stretches to increase the mobility in my leg? Can somebody help me please?