Is a doctor's helping a student in an exam considered cheating? And does that entail the unlawfulness of the university degree and the money earned from working with it?

You have done well by regretting your cheating, and whoever repents, Allah accepts his repentance. This will not affect your degree or your job, as long as you have stopped cheating and repented from it. As for the assistance given to you by the two doctors, if it was part of the cheating, then it is forbidden, and all of you must repent. But if it was legitimate assistance, then there is no harm in that.