Usually, if it's not associated with bleeding or spotting, it can be okay. I had a lot of pain early on in this pregnancy: back pains, cramping, and even spotting. I am just about 23 weeks along now and everything is fine. But if I am ever concerned and just not feeling right, I give a call to my midwife and I get checked out to be sure all is okay. Always better to be on the safe side.
U may have a uti I would call the ob and let them know just to be safe. Some cramping is normal during early pregnancy, had a ton this pregnancy but very little with my other two. Good luck.
It is quite normal to have back pain during pregnancy some get it worse then others, if it is really bad try to rest as much as possible and make sure you mention it to your doc when you have your next app. Good luck.