Nipple leakage

Does anyone else have any tiny bit of nipple leakage at random times? I'm not pregnant or anything. It doesn't have any color to it, I was in my gown last night without a bra and I felt something wet and checked and it was a tiny spot wet where my nipple was in my gown, I squeezed my nipple and nothing came out. It seems to happen some months maybe a week or less before my period. Not every month. I had a checked up last month and the doctor checked my breasts and didn't feel anything abnormal. Is this normal for some women? I don't noticed it when I'm on birth control. I'm not on it now but when I was I didn't notice it.