Megan Fox has such big arguments with her on/off boyfriend Brian Austin Green she regularly threatens to kill him.

…Charming….

The brunette bombshell — who recently reunited with the actor after breaking up in June — admits their fiery relationship is peppered with arguments.

“My temper is ridiculously bad. I’ve had to say to Brian, ‘You have to go and stop talking to me, because I’m going to kill you. I’m going to stab you with something, please leave.’ I’d never own a gun for that reason. I wouldn’t shoot to kill. But I would shoot him in the leg, for sure,” she reveal in the October issue of Rolling Stone Magazine.

Although her new horror film, Jennifer’s Body — in theaters Friday, Sept. 18 — features the star as a demon-possessed high schooler who has to eat boys to survive, it was a kissing scene with co-star Amanda Seyfried that frightened Megan the most.

“Amanda was not excited about having to do it, but I went for it,” Meg told the mag. “Clearly I can’t argue that it’s not gratuitous, because it is. We both look like children, so it looks like crazy kiddie porn. There’s no music – it’s just silence and the sound of spit. I feel weird watching it. It was just really uncom­fortable. I felt like I was witnessing some­thing I’m not meant to see.”

She Was A Cutter: “Yeah, but I don’t want to elaborate. I would never call myself a cutter. Girls go through different phases when they’re growing up, when they’re miserable and do different things, whether it’s an eating disorder or they dabble in cutting.”

Megan On Insecurity: “I’m really insecure about everything. Self-loathing doesn’t keep me from being happy. But that doesn’t mean I don’t struggle. I am very vulnerable. But I can be aggressive, hurtful, domineering and selfish, too. I’m emotionally unpredictable and all over the place. I’m a control freak.”

Check out her entire interview in Rolling Stone…