Pre term labor

I have a question... I am currently 28 weeks and since yesterday I've had cramping in my lower abdomen. Somewhat like menstrual cramping. I do have lower back pain as well but I've had this since about 14 weeks. This morning I noticed my stomach looked a little lower and I now feel like he's just sitting on my bladder. Has anyone experienced this and it be pre term labor? I don't want to go into the ER for them to tell me it's normal. I know everyone is different just want to get some opinions first. The cramping has subsided so just want to get some suggestions.