Back labor vs SPD pain

I’m having a sweep next week and my midwife also recommended nipple stimulation to get things going. So, whilst in the bath today I gave it a go and after 5 minutes I started to get really intense pains across my lower back, minor ache at the front. I do t think my tummy was having any tightenings so I’m not sure if they were actual contractions. I’m just a little confused, all stopped a few minutes after I stopped nipple stimulation..., can early back labor feel like SPD pain? Because it wasn’t that dissimilar....