If you have sincerely given your life to Jesus and are trusting Him alone for your salvation, then God has promised to forgive you–and He cannot lie. The Bible says, "This is the testimony: God has given us eternal life, and this life is in his Son. He who has the Son has life" (1 John 5:11-12). That includes you! The key is to depend not on your feelings, but on facts–the fact of Jesus' death and resurrection for you, the fact of your commitment to Him, the fact of God's promise to forgive you. Feelings come and go, and they can deceive us. But the facts of God's Word don't change, and you can depend on them. Don't focus on your feelings, but focus on Jesus Christ and what He has done for you.
Imagine for a moment that you had a very wealthy relative, and one day you received a call from an attorney telling you that she had died and left you a million dollars. What would you do? You might say, "Oh well, it can't be true"–but would that be wise? Instead, you would probably accept by faith what he had told you, and then begin to act on it.
In a far greater way, Jesus Christ offered you a gift–the gift of salvation–and you have accepted it. Now act on it! Begin by thanking Him for saving and forgiving you, and then seek to live for Him every day.