Its Ramadan &16days since last period.Next period is due in 7days time but am spotting now.Do I continue to fast until the day of expected period date?
No, since you have experienced a gap of Tuhr (i.e. 16 days in your case of purity), the spotting now will be regarded as Haydh. You should discontinue fasting as this is now your Haydh period.
and Allah Ta’ala Knows Best
Mufti Muhammad Kadwa