Please help me!!! I don't know how to do...

At first, I have no any problems while I am playing Halo 4. However, I recently experienced lagging while I am playing multiplayer in Halo 4. The problem is getting worse. Now, it even says that the Halo 4 server is not available and I am not able to play any multiplayer games, spartan ops and even co-op campaign with my friends. I can now only play campaign solo >.<… I noticed that my friends have no issues on that so I would like to know if someone also experienced this problem… and what can I do for that??? It’s almost two days!!! Thank you!!!