Engorged breasts + milk flow at 39 weeks??

I’m 39+2 and lately my breasts have been killing me. I have two kids already that I breastfed for 2 years, so I know what the let down feels like, I get that anytime even my shirt rubs my nipples. This morning I woke up and had that sensation, but afterwards my breasts felt sooo full and painful, so I hand expressed and it was a milky mess. I’m convinced my milk has come in? I guarantee I could have easily pumped an ounce or two had I actually pumped or continued hand expressing. Has anyone else had this happen? I’m worried baby won’t get the proper colostrum now ☹️ it was definitely milk. Could it be a sign of labor? I’ve lost my plug and had bloody show this morning before this happened as well. Should I call my doctor?