Will a home pregnancy test be positive in the fourth month? it's been 16 weeks since anything happened, neg tests but irregular periods.

Yes: Some causes of a late period include: excessive weight loss or weight gain, increased exercising, emotional stress, having an illness, traveling, medicines (like birth control pills), hormonal imbalances, etc… Seeing a doctor is a good idea if symptoms are worrisome or if periods are always irregular. A pregnant woman's preg. test is positive 3 weeks after sex, and is positive if retested later.