Question:
If I don’t think I always had 2 knots at the end of my tzitzis, did I do the mitzvah of tzitzis when wearing those pairs of tzitzis?
Answer:
Ideally, we should have five sets of two knots each, however if the last set unknotted, which happens often, the tzitzis are still kosher to wear, and you were yotza the mitzva. Understandably they should be re-knotted (but not on Shabbos), however they are still kosher the way they are.
Best wishes
Sources:
M:B 11-65.
