Sore???

How can I tell the difference between sore tatas and sore pecks? I just started working out a month ago but my “boobs” have been sore for around 4/5 days now and I’m praying that it’s just the muscles because the last time my boobs hurt I was pregnant. My period is a week out so it’s too early to test to calm my nerves. And I am on birth control. But if there a way to tell the difference?