welcome to Healthcare Magic.
Delayed period may be due to thyroid imbalance. As you are known case of hypothyroidism
and medicine dose just increase to 100mcg from 50mcg.
First, In your case get your thyroid profile (serum T3/T4 and TSH level
) done to rule out hypo or hyperthyroidism
. Both these condition lead to menstrual imbalance.
Concurrently get evaluated by general physician to rule out other cause of delayed period like pregnancy
Wish you all the best.
Dr Ashish Kumar Mittal