Hi, I'm 18 and I feel like I have already ruined myself for eternity. You see a few months ago I was working with some women who needed help. They needed someone to be a better man than they had ever seen because all they were used to were men who wanted sex. So I decided then and there that I would become that better man, and I started living for God...I was on a quest for truth and enlightenment so I could help them out. Well, somewhere along the line I faltered, turned around after I put my shoulder to the plow, and after I had tasted that heavenly gift of living for others. And now I am in the worst state I have ever been in. I can't even think straight now...or meditate on God's word...because I feel as though I have blasphemed the Holy Ghost. Is his what it means to have done the unpardonable? I mean I was seeing beauty in simplicity and God was everywhere and then I went and turned to living for myself again and now I'm dead again. Is there no way to get back? I really think that God wanted me to be something real important and to be in heaven but I failed my entrance exam. The bible is pretty clear on this but I just keep thinking that there has to be a way...like all the things I learned and the joy God gave me can't be in vain...Are there no exceptions? Am I doomed to an eternity without God? I was crucifying the flesh and all that out of love for others but now if I tried to follow God again wouldn't it be like crucifying the son for myself and putting him to open shame? This feels like hell that I'm in right now.
Some of your questions I have answered previously (blasphemy.html), but I will summarize that answer for you. If you are worried about having committed the "unpardonable sin" (not a biblical term), you probably haven't. Matthew 12:22-37 is the passage dealing with blasphemy. It designates two things that will not be forgiven. One is "blasphemy of the spirit" which is most likely believing in one's core being that God doesn't exist. You have clearly not committed that blasphemy. The other is "speaking against the Holy Spirit," which the context shows to be claiming that the Holy Spirit, the word of God, is not from God but from Satan. Your question shows that you believe the Bible is the word of God, and so you are clearly not guilty of this sin either.
You also quote Hebrews 6:6 about crucifying Jesus again and putting him to an open shame. Again I am not sure that you have fallen away to the extent the scripture is talking about. The passage basically says that if one has, after becoming a Christian and knowing the joys of that, turned his back totally on Christ so that he says what he once enjoyed is worthless, then the same arguments that brought him to Christ in the first place won't work again. This is because he has put himself in the position of those who crucified Jesus, claiming he was not the son of God. If you have reached that level, saying that everything you once believed about God and Christ was all a lie, then it is going to take more to convince you of the truth than it took the first time. Based on your question I don't think you have reached that low point.
Any sin is a slap in God's face. Any of us who have been raised from the waters of baptism into a new life and subsequently sin willfully are in danger of falling away. However, there is hope. If we "walk in the light," (1 John 1:7) then Jesus' blood continues to cleanse us, even if we sin. Although we may occasionally participate in the "darkness" of sin, our lifestyle is that of obedience and righteousness, and God's grace causes him to forget the sin. If we willfully choose to sin, knowing it is wrong and saying we will do it anyway, we can still return to the light. In Acts 8:14-25 we read of Simon the Sorcerer. He had believed and been baptized. Yet greed got the best of him shortly thereafter. Peter told him to repent of his wickedness and pray for God's forgiveness. He didn't say he needed to be baptized again to have his sin washed away. That had already happened. Subsequent sins apparently needed only repentance and prayer.
You still know the potential joy of obeying God. Concentrate on that and not on the sin which so easily besets us. When you have trouble meditating on God's word, then try even harder. What you may be experiencing is the devil, who knows you haven't crossed the line back to his side yet, trying his hardest to get you to take the step. The more you fight him, the easier it will be to resist him. "Submit yourselves therefore to God. Resist the devil, and he will flee from you. Draw nigh to God, and he will draw nigh to you. Cleanse your hands, ye sinners; and purify your hearts, ye double minded. Be afflicted, and mourn, and weep: let your laughter be turned to mourning, and your joy to heaviness. Humble yourselves in the sight of the Lord, and he shall lift you up." (James 4:7-10)
I hope this helps. You are not doomed to an eternity without God. There is still hope as long as you have breath.