OK! Exclusive: J.Lo Having Twins — Confirmed!

After months of the "is she? or isn't she?" controversy, , 38, is set to announce her impending motherhood during one of her upcoming concerts — perhaps as early as her Madison Square Garden concert in NYC on Oct. 7. More importantly — La Lopez has a bigger surprise up her sleeve — she's having twins!

"Jennifer is having twins, and she's over the moon about it," a source close to the singer reveals exclusively to OK!. "She is absolutely glowing with happiness. She's spending time relaxing with Marc and enjoying being pregnant, which is something she has always wanted."

The babies will be Jennifer's first (and second) children, and numbers four and five for the fertile . And although the babies' genders are not yet confirmed, one can only hope for two little lady Lopez's in training.

Ay, mami!