Ok... Take a read through this when you get a chance, and if you have questions please ask: http://www.sqlservercentral.com/stairway/73776/ (Yes, I know it's long)
Also, if your backups start to grow again or the used space in the log starts to grow and doesn't reduce after a few log backups, post back and I'll help you diagnose what's going on.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability