I'm contently in pain or injured or barely have provisions to provide for my family. Could this be due to sins that I may have committed or could it be a test from the greatest Allah to purify me. What does Islam say that I can do to improve myself; like Du'a or anything Halal.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. Allah, the Exalted, puts to test some of His slaves to distinguish between the good and the bad the honest and the liar. Allah Says (interpretation of meaning): {Do people think that they will be left alone because they say: "We believe," and will not be tested. And We indeed tested those who were before them. And Allâh will certainly make (it) known (the truth of) those who are true, and will certainly make (it) known (the falsehood of) those who are liars, (although Allâh knows all that before putting them to test). }[29:2-3]. He also Says: {Allâh will not leave the believers in the state in which you are now, until He distinguishes the wicked from the good….}[3:179]. Therefore, a believer has to be satisfied with the Divine Decree of Allah and should not show any dissatisfaction; whoever becomes content with Decree of Allah, Allah will grant him satisfaction, and whoever becomes dissatisfied with the Decree of Allah, Allah will make him dissatisfied. Sometimes, Allah puts someone to test in order to upgrade him. As mentioned in a Hadith: Any fatigue, or disease, or sorrow, or sadness, or pain, or distress that befall a Muslim, even if it is only the prick he receives from a thorn, Allah expiates some of his sins for that . Another Hadith reads: When the Prophet (peace be upon him) was asked which people suffered the greatest affliction, he replied, "The prophets, then those who come next to them, then those who come next to them . Sometimes Allah even afflicts someone with trials due to his/her sins as reported in a Hadith that the Prophet (Sallallahu Alaihi wa Sallam) said: A person is deprived of his provision due to his sins . [ Ahmad ]. Knowing whether the affliction is due to the sin or merely a trial by from Allah is not necessary. The important is to be patient in the face of catastrophe and hard times, to seek forgiveness from Allah, to make repentance and to implore Allah's Mercy to remove calamities. As for useful supplication to get Allah's Mercy and blessings, it needs details. However, we advise you to read the book "Hisn al-Muslim" which is translated in English. You may find in that book a good collection of the supplications that should be recited according to the different occasions. Allah knows best.