Need assistance suing my ex for medical bills incurred from him assaulting me

Unfortunately the first question that we have to ask is "is your ex collectable"? By that, I mean does he have any money or the prospect of future money to compensate you. This can sometimes be answered if there is any kind of insurance that he has, typically homeowner's insurance, that might cover assault if you were to bring a claim. If he doesn't have assets or insurance that would cover this, there is really no point in bringing a civil claim and you shold proceed with a criminal complaint.