it say i am already playing...

Put the summary of the bug you're having here
at org.lwjgl.opengl.WindowsContextImplementation.create(WindowsContextImplementation.java:50)
at org.lwjgl.opengl.ContextGL.<init>(ContextGL.java:132)
at org.lwjgl.opengl.Display.create(Display.java:850)
at org.lwjgl.opengl.Display.create(Display.java:757)
at org.lwjgl.opengl.Display.create(Display.java:739)
at bsu.am(SourceFile:523)
at bsu.aj(SourceFile:352)
at bsu.a(SourceFile:299)
at net.minecraft.client.main.Main.main(SourceFile:120)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at org.lwjgl.opengl.WindowsContextImplementation.nCreate(Native Method)
at org.lwjgl.opengl.WindowsContextImplementation.create(WindowsContextImplementation.java:50)
at org.lwjgl.opengl.ContextGL.<init>(ContextGL.java:132)
at org.lwjgl.opengl.Display.create(Display.java:850)
at org.lwjgl.opengl.Display.create(Display.java:757)
at org.lwjgl.opengl.Display.create(Display.java:739)
at bsu.am(SourceFile:523)
at bsu.aj(SourceFile:352)

– Initialization –
Details:
Stacktrace:
at bsu.a(SourceFile:299)
at net.minecraft.client.main.Main.main(SourceFile:120)

– System Details –
Details:
Minecraft Version: 1.8
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_60, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 100365064 bytes (95 MB) / 159076352 bytes (151 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.8
LWJGL: 2.9.1
OpenGL: ~_ERROR~ RuntimeException: No OpenGL context found in the current thread.
GL Caps:
Using VBOs: No
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: [Grim Skeleton Dog]
Current Language: ~_ERROR~ NullPointerException: null
Profiler Position: N/A (disabled)
What I expected to happen was...:
Describe what you thought should happen here

What actually happened was...:

1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...