Labor signs?

Tasha • Married to my high school sweetheart 💖 With two beautiful babies! 💖💙 Pregnant w/ #3 🥰
I'm almost 39 weeks. I'm having cramps like I'm on my period, backache, and I ate like 1 or 2 hours ago, had that full feeling, and it went away.. than came back & is hurting me honestly. What do I do? The cramps and backache have been happening for 2 days. Please reply fast.