I gave up a lot of my dreams when I found out I was pregnant at 18 and my parents said I had to marry the guy and have the baby. They wanted a baby. They got a baby. I got kind of pitched by the wayside once she was born. Things went downhill from there.
Now, I'm almost 50 years older, and looking back I still could have followed my dreams. She could have come along with me. It would have been more difficult to accomplish but it could have been done and I may have saved her from the mess that was made of her life.
Follow your dreams and take your son along. Live in an efficiency apartment if that's all you can afford. Get loans. And just love him. And be the doctor. A PA is fine but why not go for what you dreamed of? Or become a PA and keep going to school for your MD.
Don't get old and regret what you could have been. Do it now while you are still young.
One life. One chance. Make it count.
This is just my POV looking back. Others have some good ideas.