Brown spotting/clotting in pregnancy?

I have a question. Im 6 wks, went 5 days ago for a sonogram and saw the sac...when I went to the doctor he did a pelvic exam and said that I had a bladder infection, put me on antibiotic and said that in my vaginal secretions i was spotting and not to have sex. i haven't been having sex but ever since the exam ive been having light brown spotting. well out of nowhere tonight, just sitting down i had a tiny small dark dark brown clump (size of a dime maybe) come out, and now im not spotting or anything i wasnt cramping or anything so its weird. could this be normal? i know its not a tubular cuz my sonogram. i have a apt in the morning but just freaking out now.