Can a 1cm. uterine fibroid cause spotting (even while taking-prometrium) and lower abodominal pain?

I had an ultrasound which told of the 1cm fibroid and having been taking prometrium 100 mg. for just over a week (at night). Just had some spotting yesterday - Sat.-(which starting the testing and medicine about a month ago). I have lower abominal pain which comes and goes but has been around for a few weeks.

Yes, it could but the medication you are taking could also be causing this. I've talked to a few women that tried Prometrium and had a problem with spotting and also some abdominal pain. I would recommend getting back in touch with your doctor to let them know what's going on so that they can evaluate the situation further.