Pain in the evening

Imogen

I was wondering if anyone had experienced this? I’m 18 weeks and since Monday I have pain every evening, lower back pain that wraps around to my belly, kind of crampy. It’s not excruciating but very uncomfortable, I lay down as soon as I get uncomfortable in the evening and it takes a good few hours to subside. Is this just normal for twin pregnancy? I’m just worried because I had pre term contractions with my last baby at 28 weeks