Start of labor? Period like cramping? Contractions?

I’m full term and have been having some back aches and cramping for the past few days. Today they feel more like period cramps but not consistent. I also have a lot of pressure in my pelvic area. It’s been like 5 hrs if I had to guess that they seem to come and go in waves. Maybe 30 mins apart?? Can this be the start of labor? If so how long did you have just cramps before actual painful contractions started to where you timed them?