I’m contracting can’t feel it?

So I went up the hospital earlier and they hooked me up to a machine for baby heart rate as it went up to 170 ( me and baby are both home and fine ) but when I was hooked up to the machine the midwife came in and was like oh can you feel the contractions? I said no at that time I couldn’t feel them but earlier on I felt tightening in my belly and back but thought it was because the baby was being extremely active (the reason her heart rate was so high). What does this mean im 39 weeks and 1 day. Why am I contracting but can’t feel all of them? Am I close to labour? Has this happened to anyone else?