Not lactating, but…?

So I breastfed my youngest two for 2+ years. My youngest is now almost 6… so I haven’t lactated in a few years now 😂 but over the past week or so, I’ve noticed something. I get this random full feeling in my breasts, and it feels like I’m having a let-down. They’ve been REALLY SORE lately, too. I just had what I believed to be my period last week. I’ve taken tests and I’m not pregnant according to the home texts. (My primary is doing a blood one because of other symptoms I’m having just to make sure, I should have that back tomorrow!) I’m just confused as to what could be causing that? Could birth control cause it? I don’t THINK I’m pregnant. All urine tests have been negative as far as I could tell. (Maybe a faint line, but nothing that just stood out.) what could be making me have this feeling? They seriously hurt! 🤣