Stopped breast feeding and leaking again

So I stopped breast feeding almost 3 weeks ago because my supply was low and I returned to work. I also got a ton of breast milk donated to me. I had no problem stopping because my milk was pretty much gone anyway. No engorgement or pain what so ever. Well now in the last day my boobs have started hurting really really bad and tonight they started leaking constantly. It is like the first few days all over again. If I’m not wearing nursing pads it’s soaking my shirt and running down my chest. I don’t think I’m pregnant because my husband and I haven’t had sex since my last period. I think my period is late though. Does anyone have any idea why my milk went into over drive again. Could it just be that my period is going to start?