Nipple discharge?

Ka

I was doing a self breast exam and I squeezed my nipple a little and a tiny bit of liquid came out. I have the Mirena IUD so idk if that’s a side effect or if it’s normal? I’ve had this happen before I didn’t turn out pregnant or anything. It’s not breast milk my daughter is 3. Is it something to worry about? I don’t have any weird lumps in my breasts. I’m supposed to start my period around this time and my boobs are sore like I’m going to start.