Violent Pain In Leg My Kitty Is Limping But She Keeps Switching Legs -back And Forth Between Right & Left Back Leg. What To Do?

My kitty is limping but she keeps switching legs -back and forth between right & left back leg. What to do? - violent pain in leg

It is inside and out, but only 2 days spent in the air (somewhat unusually for her) for a long time to remember (as strange as usually comes much faster.) It has long been limping again, and I realized that Today, in fact, favored one leg, then another. It comes and goes, seemingly at random. I went through the legs of the two great depth and legs, is not realized in the blood, swelling, or anything on the ball. He briefly discussed the major bones and toes on each foot, and certainly not much reaction, but when I press the wrong guy standing when the events. What should I do? She's My Baby, but I'm also a little short, so I just want to spend money E-Vet cases of absolute necessity. She is eating and drinking and not get up and go, but not as strong as usual, and it's obvious pain. Thank you very much.