It must be stressed here that Islam does not give permission to the believers to do any act which is illegal or Haram, especially cheating. You are required to sincerely make taubah and beg for Allah’s swt forgiveness for your lack of judgment in cheating. However, Allah is very forgiving and merciful, and since you did not know any better at that time of ignorance and there is nothing you can do to rectify the past and since your work now mainly demands your experience and not the subjects you cheated on, InshaAllah your repentance should be sufficient and the regret you have is a great sign of sincere repentance insha’Allah.
As long as you are doing things the right way now and promised Allah swt to never go back to cheating to acquire higher knowledge or degrees, then Allah will accept your repentance and forgive your past mistakes of cheating on your tests to acquire your degree, and your income, by the mercy of Allah, will be Halal inshaAllah.
Allah says in the Holy Quran Chapter 3 Surah Ale Imraan verse 135-136: Allah likes such good people very much, who, if ever they commit a base deed or wrong their own soul by the commission of a sin, remember Allah instantly, and ask for forgiveness from Him for their shortcomings. For who, but Allah, can forgive sins? (And Allah loves those) who do not knowingly persist in the wrongs they did. These will be rewarded with forgiveness from Allah, and with Gardens beneath which canals flow, and they will reside therein forever! How excellent is the reward of those who do good deeds!