Could i have had a miscarriage? what are the chances?

It sounds like you took all the precautions. If you were taking the antibiotics when u had and there was a problem with the condom, i would worry. You are safe. Plus- you would have to be alot more pregnant then two weeks to have had a miscarriage with results like that. At that soon, if you had a miscarriage, you wouldnt even know it. Its common. It sounds like a really nasty period plus pain from bronchitis, and stress. No worries. But if it makes you feel better, take an OTC preg test. Good luck!