Minecraft Teleporting back to where i died?

You screwed, unless you wrote down the coordinates in case something happened or slept in a bed in your castle or have a mod beforehand that will prevent this or even placed some landmarks your just screwed

If you're on Minecraft pc do /back

Yes, technically there are two ways. However you have to do a command at the place where you would like too re-spawn every time you die. The first way, you must have slept in a bed. What this does is it sets as your home and re spawns you there after every death. The second way is to type this command in. What it does is it allows you too respawn where ever you are standing at the time of the command. The command you have too type in is called: /spawnpoint Nonetheless if you are looking for your castle, I would advice installing the Rei's mini map mod. This allows you too generate structures through a mini map at the top right of your screen. So you can look for your castle that way. Hope this helps