I was catholic and converted to christian,is there a way i can go back to catholic?
Unless you were excommunicated, you are still Catholic. Just return to the Church, do your Confession, partake of the Mass, and you're back on track.
No one can keep you from believing how you want to believe.... why wouldn't you be able to convert back to Catholic?
Catholics are Christian.
Yes Catholics are Christians. And yes you can go back to being a Catholic.
By your question, I feel you are not sure what being a Christian means. Christianity is faith in the Trinity - God, Jesus, Holy Spirit. it is not a denomination. Strengthen your faith in a good Bible study class or start by reading Gospels of John.