The world does not revolve around Qantas, there are many, many viable career options for pilots.
Some excellent pilots I know have problems with anything more complex than Primary School Arithmetic!!
Skill and tenacity will achieve far more in a flying career than maths and physics - although all four helps.
If Qantas is your sole goal you should face reality and perhaps quit now - I don't know the statistics but my guess around one in a hundred Qantas applicants actually scores a gig at Qantas.