Almost time?!

Yesterday I was checked at my ob appt (39w4d) and I was 90% effaced and 1.5 cm dilated. Baby was crazy active for 3+ hours or so last night before bed. This morning (and throughout the night) my belly was really tight with backaches. I felt cramping and felt like I had to poop. I went to the bathroom around 7:30am and had a large BM (had a large one yesterday as well when baby was very active). I went to wipe and realized I lost my mucus plug on the toilet paper (all at once I think). Since then, I've had mild contractions that I thought were braxton-hicks just more severe.... they are lost abdomen accompanied with vaginal cramping and intense low back ache. The cramping and back ache go away when the connection stop. They are about 1 min long and 5-6 min apart. Called ob station and updated them. I am waiting it out at home (live 4 min from hospital).... due date is Monday! I'm a ftm.... when do you think I'll have this baby?!