Any Mommas who have still been breastfeeding when they got pregnant with another baby? My period is…

Any Mommas who have still been breastfeeding when they got pregnant with another baby? My period is due in 2 days but we are trying for baby #2.....

Problem is all day today my boobs have been SOOO sore. And then every time I feed my daughter my nipples KILL me!

Any idea of its a pregnancy symptom or if it could mean something else?