Joined minecraft, cant place blocks, spread items, or eat

So I wanted to play minecraft because roblox was getting boring. So when I spawned in, I could place, and spread items in inventory. When I was going to eat, I couldn't. Then I couldn't place or spread items. I don't know whats going on. Is it a bug? Or is it just me? I don't know if it my computer but if it is a bug can you fix it? Thanks, from Joel