In the midst of a painful, drawn-out custody battle for her two sons, Britney Spears wanted to be sure of one thing — that she didn’t accidentally get pregnant again. So she began taking Depo-Provera, a contraceptive that merely requires injection of the hormonal drug every three months.

The only problem? Britney skipped her appointments. “She missed a shot in July,” says a friend of the singer, “and she was late getting another shot.”

After complaining that it made her gain weight, Britney, says an insider, quit Depo-Provera and switched to birth-control pills. “But she’s constantly forgetting where she put them and to take them,” says the insider. “She seems to find it amusing — she laughs at how scattered she is.”

And making matters worse, Britney’s been taking a mild prescription stimulant, Provigil, which can decrease the effectiveness of oral contraceptives.

Meanwhile, Brit, 25, hasn’t exactly been living like a nun. She’s slept with pal Sam Lutfi, some friends believe, and her friend claims Britney and producer JR Rotem have been “hooking up.” “When her friends ask if she’s being safe, Britney says it’s just casual sex,” says the friend. “She seems to think that just because she isn’t in a formal relationship, she’s somehow immune to getting pregnant.”

Life & Sytle