Help please... FTM

I’m 36 weeks pregnant and I’ve felt a lot of pressure down there and period like cramping all day!! Almost like I have to go to the bathroom! Just recently though I’m having some really bad back pain on my left side! It’s pretty pretty painful and constant! I’ve tried moving around, laying down, and changing positions. But nothing seems to work. Is this normal? And if so how do I get some relief??