Wow. I would have thought that the ER would at least give you a referral.
15 weeks along is NEVER too late to receive proper prenatal care.
I would ask your primary care physician for a referral or consult clinics in your area. Even your county's health department should be able to help you.
Just to let you know, my first baby's placenta was small and she was born completely healthy in every sense. No one ever recommended termination.
I'd been told I couldn't have kids so not one single person tried to steer me in that direction.
Some doctors don't readily take on new patients, but that doesn't mean you can't get the care you need.
Check into every resourse you can in your area, even women's shelters. They have access to things you wouldn't believe.
You're not the first person in this world not to realize you're pregnant and I guarantee you'll find someone to help you with your prenatal care.
Just keep checking.
I wish you the best. I wish you a healthy baby and a happy birthing experience.
Hang in there!
P.S. I worked in medical records for a hospital and you have the right to a copy of your records. You may have to go in and sign a release, but they really can't withhold things from you. You have a right to your own protected health information.
Find an advocate through a clinic or midwife. They will help you.