You are speaking of a medical malpractice claim. There are several points to consider.
First, you would only have a meritorious claim if you suffered damages. You and your twins seem to be fine. So I do not see that a lawsuit would be worthwhile. If you spent money out of pocket for all that testing and doctor's work, then you may have damages to claim - I just can't tell if you have damages that would exceed what you would have to pay in legal fees.
Second, the issue in a medical malpractice claim is whether the doctor deviated from accepted medical practices in the community. Not a big city if you don't live in one, but your local area. In fact, before you can start a malpractice case, you need to get a certificate of merit from a licensed physician who will attest that from their review of your records, your treating physician departed from accepted medical practices in the community. You might find that the way they treated you is the way most doctors in that community would have handled somebody coming in and complaining of a headache, neck and shoulder pain. I don't know because I am not a doctor and don't know the community standards, but that is a very important consideration.
Lastly, the malpractice must have been the cause of your injuries or damages. If your damages are out of pocket expenses for medical treatment, but they helped relieve the headaches, neck and shoulder pain, I'm not sure you could even claim entitlement to those expenses.
One final word. Please research the medication(s) they prescribed you, and see if they could possibly affect the health of your unborn babies. If it is something that could be harmful, then first and foremost please do what you can to verify their health. If, God forbid, something happens to them, I would certainly think there could be merit to a claim if they had prescribed medication that should not be taken by somebody who is pregnant and they never asked or verified that you were not pregnant. That is a better case that I hope you never have to file.
Best of luck.