I am suffering with patellar tendinitis and today is very bad. i can't walk. do you think i need crutches?

Depends on fall risk: If your condition is severe enough to pose a fall risk, then using crutches temporarily is reasonable. For most cases of patellar tendonitis however, this would not be expected.

If limping: If your tendinitis is worsening and is causing you to limp then use crutches or other aid(s) temporarily until you improve. Persistent limping can result in its own set of maladies including LBP, calf soreness and pes anserine bursitis. Best of Luck!