As-salaamu `alaykum
Welcome to TTI! May Allaah keep you steadfast upon the path of Islaam, ameen. I further hope that we here at TTI can help you, and that the articles and discussions here benefit you. Sister be reassured, as Allaah says in the Qur'aan,
"Verily Allaah does not forgive that partners be associated with him (shirk), but he forgives other than that to whomsoever he pleases."[Soorah An-Nisaa' 4:48]
Allaah/God says that here that He forgives all sins except one (if you do not repent for it). That one sin is shirk (polytheism), to ascribe/associate partners with Allaah in His worship or His lordship. To ascribe partners in his worship, would be to worship something or someone along with Him. Examples include praying to Jesus, or sacrificing (an animal) to a tree, or fearing an idol. To ascribe partners with Allaah in his lordship would be to state for example, that someone other than Allaah is your creator and cherisher, or to give the qualities and names that belong to Allaah/God to other than Him from the creation.
This is the only sin that Allaah does not forgive. And there is only one thing that can wipe shirk away, and that is the acceptance of Islaam. As for your other sins, then they are forgiven. Despite how bad they might be, nothing levels polytheism. One could be the most sinful person, committing every sin possible, except for polytheism and still be forgiven in the blink of an eye. Yet one could do every good deed, but at the same time associate partners with God. In this case we believe that such a person, despite his good, has lost all of his deeds because of the partners he associated with God.
And it has been revealed to you, and to those before you, that if you commit shirk, all of your deeds will be destroyed, and you will be amongst the losers."[Soorah Az-Zumar 39:65]
Regarding forgiveness, then three deads (to my knowledge) wipe away all of ones sins and they are a) to accept Islaam, b) to have an accepted hajj/pilgrimage and c) to migrate from a non-Muslim governed land, to one governed by Muslims.