Pains

I’m a FTM and 37+3. I’ve been having really bad back ache since lunchtime today it’s caused me to cry 4 times now i haven’t experienced it this bad during my pregnancy. I’ve felt my baby move a lot but also felt my stomach go tight but now i’m struggling to know if it’s my stomach tightening or baby moving?? i know it sounds stupid because i should know the difference but there’s just so many symptoms in pregnancy and so much to look out for. I’ve also been having really bad pelvic pain today it’s been hurting to walk all day. Could this be a sign of labour approaching do i contact midwife?