I took a penicillin shot yesterday and i think i am having an allergic reaction. bruises,confusion,weakness...help?

Seek A Physician: This reaction sounds abnormal for an allergic reaction (wheezing, hives, itching etc.). There are other rare immunologic reactions from medications (serum sickness, Stevens-Johnson syndrome) but these do not perfectly fit these symptoms. If you are having confusion and weakness I think it is important that you seek urgent medical care for further evaluation.

Jarisch-Herxheimer: Based on your age I'll take a chance and assume you might have received the penicillin shot for Syphilis? If so you may be having a reaction known as a "Jarisch-Herxheimer reaction" which occurs from the death of the bacteria causing syphilis. Talk to the doctor who's treating you.