Good evening. There is no evidence which startes that post covid you will have sensitivity. You need to visit your nearby dentist to evaluate the exact cause. May be the teeth which were restored(filled) previously may have some secondary caries or issues related to tooth brush abrasion. Sensitivity is something which is not related to lactation as well, and neither related to the oral
calcium intake. Hence it would be our suggestions, do not ignore and visit a nearby dentist as soon as possible. So that the things are evaluated clinically. Thank you.