Hi 369Monkey,
If your girl had miscarried, she would have lost lots of blood and experienced some blood clotting with pain. Perhaps, for whatever reason she told you she was when she wasn't pregnant. It is very unusual for a doctor or his professional staff advertantly give a patient a birth control shot without asking if they are pregnant or giving a pregnant test or asking when was their last period. The doctor and his staff only go by what the patient says, if the patient says they had their period at a certain time that is what they go by. You didn't mention how old your girl is but by you being 18 you have the rest of your life ahead of you. I agree with you, with all the things you should be at that age, a Father isn't one of them. I applaud you wanting to be responsible and stepping up to the plate had you became one. Now, I don't think you are but you very well could be if you and your girl continue to do parental sexual acts without protection. Take some good sound advice and don't trust having sex with your girl again, she just may want you to be a Father when you don't want to be. Finish school, go to college, and some day wipe your brow and say, "Whew, that was dumb."
Good Luck,
Faded Rose