The other day I was struggling with sin and I told God that if tomorrow I committed this sin that I want it to be unforgivable. I did this so I would think twice when I was tempted. In the end I committed this sin, even though I told God not to forgive me this time. Can I still be forgiven now since I did committed the sin anyway?
Since when do people get to tell God what He is or is not able to do? Moses once was frustrated and asked God to remove him from God's book of life: ""Yet now, if You will forgive their sin-but if not, I pray, blot me out of Your book which You have written." And the LORD said to Moses, "Whoever has sinned against Me, I will blot him out of My book"" (Exodus 32:32-33). God's response to Moses is that He makes the rules, not Moses.
You are not to sin because God said sin is wrong. Your request of God was meaningless and did nothing about the actual problem. It might have made you feel like you were working on the sin, but you never addressed the real issues. "These things indeed have an appearance of wisdom in self-imposed religion, false humility, and neglect of the body, but are of no value against the indulgence of the flesh" (Colossians 2:23).
Face the fact that you've sinned and that you have changes to make in your life. Learn what those are from God and start doing them; instead of wallowing in self-condemnation. See: Are You Unforgivable?