Flash glitching

Hi I have been having this flashing glitch issue and it won't go away at all and I have done everything other people have suggested. I am really getting tired of it. Please help me. It starts to glitch out the trees, mountains, houses, grass, water, etc. It happens on the mulitplayer server at my house. My husband and brother-in-law don't have this issue at all. What should I do? Please help me. Also found out it is even in single player.