SQL Server 2014 Negative log. Stuck at CHECKPOINT. Unable to do anything

I have a database that is stuck at **CHECKPOINT** for hours and I already tried all solutions that have been suggested in this site with no avail and I'm starting to lose faith. Keep in mind that the database is not in recovery, emergency or anything. I'm able to query the tables just fine. The only difference I've noticed between my problem and the other questions is that the "available free space" when I try to shrink the log is negative (-0.24MB). **How did it start?** The server had a task that made a backup of the database at midnight. The problem started when the server ran out of disk space. I've already free up some space. **I already check:** 1. Disk space. It had zero now it has more than 150GB available (more than enough since he database is relative small) 2. No transactions are running 3. No users are connected 4. No replication 5. Database Recovery mode is **SIMPLE** (always been) 6. Max size for log is unlimited **I already tried unsuccessfully:** 7. Creating a new log file 8. Increasing actual log size 9. Shrink log file (I've noticed that the "free space" is negative. It says -0.24MB) 10. Repairing with DBCC 11. Restarted the server and SQL Server Service 12. Disabled all tasks (SQL and Windows) 13. Executing CHECKPOINT command twice 14. "No checkpoint has occurred since the last log truncation, or the head of the log has not yet moved beyond" if I ran the query from Troubleshoot a full transaction log I can't do anything because it always responds with "Transaction log is full due to checkpoint" Any ideas?