Hi mama! Yan looks like bloody show na, especially with the mucus and color you're describing, a lot of the moms in our group experienced similar discharge around this time, usually a sign na the cervix is starting to change na talaga. Since you're already 3cm dilated, having occasional cramps and back pain, and you're almost 39 weeks, your body is definitely preparing for labor, pero I'd really suggest calling your OB or going to the hospital para ma-check properly kung yan na talaga ang mucus plug or if there's anything else happening na kailangan i-monitor. Better to be safe, lalo na at may discharge ka na like that, walang hassle ang OB, mas mapapahinga ka lang ng isip mo once you hear from them directly.