TNT tries to kill you

Note: This happened in Minecraft 1.8.7. I was playing my world. I put a TNT a block in front of it and i put a button. I had diamond armor. I activated the TNT. It exploded 3 times! And there was no TNT around! I'm sure. I tried it 10 or so times and it happened again! Also I tried exact same thing but i activated it and ran out. It exploded one time but when i went to the explosion area i exploded again. It stops when it kills me. It only worked in survival mode. And it only happens in that world. I have no idea what happened. It was on a singleplayer world. No LAN.