Blood in urine test, what could it be?

Last night i had this horrible pain in lower left stomatch side and straight accross to my back. (My lower left side) and i couldnt sleep because of it and this morning i woke up worse . But then i drank a advil and it calmed it down. Im now just getting pains sometimes. I just got back from the doctor and he said there was blood in my urine test,( i couldnt see it) it burns when i pee. And my blood test results are coming in tomorrow or thursday. 
​My boyfriend came alittle bit inside of me, on the day my period ended ( or the day before it ended i dont rememeber ) 
​So my question is ,
​What might be wrong with me?  Is there a chanse im pregnant? Or just have an infection? Or something more serious?