May I recommend reading 1 John- all of it. But first pray and ask God to help you understand, He wants you to be assured of your salvation. 1 John 5:13 "I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life." A wonderful book on the subject is "Absolutly Sure" by Steven J. Lawson. To help me build my faith it was recommended to me to read Romans 4 everyday for 20 days. It so helped me. I'm praying for you!