Back to back Pregnancies

Does anyone have experience with back to back pregnancies and preterm birth? I am on my 4th pregnancy (oldest is turning 3 in Nov) in a row and thankfully all of my boys were born healthy and full term but with this pregnancy (currently 30 weeks) my symptoms have been ALOT worse ALOT earlier (cramping, pelvic pain/pressure, sharp abdominal pain, dull lower back pain) and I'm nervous about preterm labor and if I will know it's happening. Does anyone have experience with this?