which steroid did they put you on? I work in a pharmacy and might be able to help. I would think that the pain med would be gone for sure and the antibiotic probably too. there are a couple of antibiotics that remain in the system for about a week after stopping them, but those that I am thinking of are regularly prescribed while pregnant (I know because I have been there and done that). I wouldn't let the strep stop you! When I was ttc baby #2 I had a yeast infection the month I got pregnant. My doc said to just look at the benefit and risk and decide which was more important! I'm no MD, so I would double check, but I bet you are fine! Good luck!
The pain shot would be out of your system by the time you and I'm pretty sure the antibiotics would, too. The only one I would be terribly concerned with is the steriod. Try googling the name of the steroid and see what the indications are for pregnancy.