I am the same. Sometimes I just wish my metabolism would slow down... You can only eat so much.
Firstly though, it doesn't sound like you are getting enough sleep for growth. 5 hours really isn't enough to build muscle. Shoot for 8 hours, at least.
Secondly, how OFTEN are you eating? Eating a solid meal of starchy carbs and a protein source every 2.5 hours is ideal. Skipping just one meal can be critical and cause catabolism. Also make sure you are getting 400 - 500 calories of whey protein and carbs in your post workout shake before eating a solid meal within an hour of starting the shake, and eating breakfast with a protein source as soon as possible after waking up in the morning.
Some may find this extreme, but another thing I found to help was getting some calories in the middle of the night (don't set your alarm for it, but if you wake up due to nature's call then down a shake in the middle of the night). If you are an ecto you will burn lots of cals in your sleep, so a shake in the middle of the night is key.
Finally, if you are certain your diet is in check, perhaps you should consider taking a couple of days off training or at least lower the workload to allow your muscles to recover?
If you are still really frustrated you can also look at supplements.
One final thing, if you are still young, take heart... your metabolism does slow down as you get older.