Hardening the Heart
You said that "lately" you have trouble feeling repentent. This means that in the past, you DID feel repentent.
The sin of blasphemy against the Holy Spirit does not lie in any sudden word or deed; it is the firm, determined resistance of truth and evidence. It is not that God sends out a decree that man shall not be saved. He does not throw a darkness before the eyes which cannot be penetrated. But man at first resists a motion of the Spirit of God, and, having once resisted, it is less difficult to do so the second time, less the third, and far less the fourth. Then comes the harvest to be reaped from the seed of unbelief and resistance. On the other hand, every ray of light cherished will yield a harvest of light. Temptation once resisted will give power to more firmly resist the second time; every new victory gained over self will smooth the way for higher and nobler triumphs. Every victory is a seed sown to eternal life. God destroys no one. The sinner destroys himself by his own impenitence. No one need look upon the sin against the Holy Ghost as something mysterious and indefinable. The sin against the Holy Ghost is the sin of persistent refusal to respond to the invitation to repent. There is no . . . hope of the higher life, but through the submission of the soul to Christ.
Every act of transgression, every neglect or rejection of the grace of Christ, is reacting upon yourself; it is hardening the heart, depraving the will, benumbing the understanding, and not only making you less inclined to yield, but less capable of yielding, to the tender pleading of God's Holy Spirit.
Many are quieting a troubled conscience with the thought that they can change a course of evil when they choose; that they can trifle with the invitations of mercy, and yet be again and again impressed. They think that after doing despite to the Spirit of grace, after casting their influence on the side of Satan, in a moment of terrible extremity they can change their course. But this is not so easily done. The experience, the education, of a lifetime, has so thoroughly molded the character that few then desire to receive the image of Jesus.
Even one wrong trait of character, one sinful desire, persistently cherished, will eventually neutralize all the power of the gospel. Every sinful indulgence strengthens the soul's aversion to God. The man who manifests an infidel hardihood, or a stolid indifference to divine truth, is but reaping the harvest of that which he has himself sown. In all the Bible there is not a more fearful warning against trifling with evil than the words of the wise man that the sinner "shall be holden with the cords of his sins." Proverbs 5:22.
The cure for this is to pray as never before that God will pour His Spirit out upon you, begin studying the Scriptures as never before... and when you see any duty in the Bible that God asks of you, DO IT... don't ignore it. When God sees that you are following the light, He will give you more light, more of a conscience, more sensitivity of soul. Prov:1:23: "Turn you at my reproof: behold, I will pour out my spirit unto you, I will make known my words unto you."
Jn:14:21: "He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him."
You will slowly regain your sensitive conscience back again, if it's not too late. It must not be too late, because you are showing signs that it is bothering you. If you had absolutely no conscience left, then it wouldnt bother you.