It is normal to have mild cramping and pain as your body is adjusting to being pregnant but if the pain is bad then you need to call your doctor and let them know what is going on. It's always good to contact the doctor anytime you feel like something could be wrong, but I had back pain early on in my pregnancy because I was tiny (weighed 89 pounds) and I gained weight pretty fast but it is different with everyone, so let your doctor know if you feel weird.
It is possible. Your uterus is growing to accommodate the pregnancy which can cause some cramping. If you have bleeding, or are experiencing any sign of a urinary infection, you should call you doctor. If not I would mention it at you next visit.