If I used to be a Christian does that mean I committed shirk and now Allah won't forgive me?

Before coming to Islam I was trying to find God so I studied alot of religions some with positive messages and other with not so desirable ones including satanism so does that mean I committed shirk and even tho now I'm submitting I still won't be forgiven ? Also another part is I know when you become Muslim you past sins are wiped away but does that not count for shirk?