Breastfeeding while Pregnant?

Hello ladies. I went to the obgyn on the 10th. It was my 21st b-day. I am pregnant. They did a transvaginal ultrasound and didn't see anything. He said to come back in two weeks and we should see the baby and hear the heart. Did anyone else not see their baby and the second time see their baby? He said I am probably like 5 weeks. He also said stop breastfeeding my 11 month old son. I know I should listen, but he isn't ready to stop and neither am I. I love the bond we have. I wanted to make it to atleast a year. Some obgyns say it is ok and some say no, because it can cause early labor. If you think about it women had babies close in age and only had breast milk back in the day. You would think your body knows best. I just don't know what to do. Did anyone breastfeed while pregnant and have a healthy baby?