My FB keeps sending out spam?!?

[Kenneth]

This has happened once before, and it was my fault for clicking on it. It sent out spam to all my friends. After about a week or two, it stopped. It's been a month now, and I've made sure not to click on spam, and barely go on FB at all. But now, it just randomly started posting spam. Not even regular spam, it posted a picture of spam, and tagged all my friends in it. Why is this happening? I didn't click on anything. Did I get hacked by some sort of spam program or something? Because when I went on, I had to log in again, which is strange because it's set to automatic log in. Please help,