Decreased movement?

38 w 1 day today, the past 2 days Iv had a lot of what I think is random Braxton Hicks contractions and low back aches. The cramping almost feels like in my rectum it's so low....I also have not felt the baby move barely any the past day. I know they say decreased movement is typical before labor starts, but I'm wondering if I should be concerned and call the doctor?? 2 days ago I also had any appointment, cervix was closed, baby was very active but settling in my pelvis. Can things speed up that quickly?? This is my first pregnancy so I have no idea how the end of pregnancy is supposed to work!