Does anyone's boob ever hurt? Specifically the one on the side you usually carry baby on? My left…

Does anyone's boob ever hurt? Specifically the one on the side you usually carry baby on? My left boob has been having this ache at the end of the day when I lay down and sleep on my left side. I always panic and think it's my heart but as soon as I lay on my back it goes away. I feel like my whole left side of my body is slowly falling into aches and pains. I carry my son I kid you not basically all day. He doesn't like to be anywhere, but in my arms.