pain just below the kneecap, pain on running and stairs. i imagine that jumping is probably quite sore aswell.

does sound like patellar tendinitis. maybe some patellofemoral aspects to pain aswell.

it may be that you are too acutely painful to start squats or any form of strengthening.

have you been resting, icing, taking anti inflammatories?

strengthening in important but its only part of management of an issue like this and you have to balance and progress exercises with pain response taken into account.

other things that a decent physio should take into account are biomechanics, muscle imbalances around the hip and knee, flexibility, core stability.

you havent given a timeframe for injury, when did it first occur, how, how has it progressed? what exact treatments have you had, what type of squats are you doing ie on a decline board, emphasis on the lowering phase etc.. are you trying to avoid aggravating activities while rehabbing..