FORMER Brat Packer Andrew McCarthy is adding to his pack of children at age 50 – but the prospect of re­suming diaper duty has thrown him for a loop.

The “Pretty in Pink” and “Weekend at Bernie’s” star calls his wife Dolores’ pregnancy “fantastic news” but admits he’s worried about being a senior dad.

“When I do the math, and I have, repeatedly, I will be nearing 70 – s-e-v-e-n-t-y – when my youngest child goes off to college,” he says.

Andrew, whose children Sam and Willow are 11 and 7, was dreaming about spending his gold­en years in peace and quiet. He planned on traveling and writing.

“It’s just that I was looking for­ward to a little more time to be left with an empty nest,” he recently wrote in a magazine article.

“These newly added years of child rearing on the horizon will swallow up nearly an entire decade.”

Still, he’s kept his sense of humor about it, joking: “I don’t see this situation im­proving, as I now need longer naps than my children.”

But Andrew’s lack of enthusiasm is apparently no laughing matter to Dolores.

“She told him, ‘How do you think I feel! I’m going to have to raise this baby too… not to mention give birth,’ ” said a close source.

Andrew, who tied the knot with his second wife Dolores just two years ago, would like to keep her happy.

But a New York City neighbor confided: “An­drew is really stressed about having a third child. He doesn’t know how he’s go­ing to juggle it all.”

The actor in New York City with daughter Willow & wife Dolores