Shall I go to the doctors?

Primarypoo2
So I have really bad pains in my thighs, knees and ankles a lot. I went to the docto before and she recommended a physiotherapy doctos at the local hospital, but the waiting list is 16 weeks. And it seems he pains are getting more frequent, I'm unable to do gym most of the time. But my teacher isn't taking excuses yet I can barely walk down the stairs without the pains.

I think I need to go back to the doctors to see if there's anything wrong she can see and to get a letter from her to show my teacher, then I don't have to until my legs are capable. What shall I do?
Updates
+1 y
If I move my legs they will normally crack in both knees and they would really hurt and I wouldn't be able to move them for a couple of seconds. I walk down the stairs and I hear a crack and my legs go weak and I have to sit and slide down the stairs
Shall I go to the doctors?
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