Breastfeeding and pregnant

So I went to my son's 1 year check up. He turned 1 December 26 but because of Covid he just had his appointment. While there I informed his Doctor that I am 7 weeks pregnant with my 3rd. She asked several questions but said something that scared me. " You should stop breastfeeding soon since your nutrients should go to the baby and not your milk. breastfeeding will suck all the nutrients that should go to the baby."

I haven't stopped thinking about what she said. I've already thought about stopping BF but hasnt been easy but I want to stop now more than ever.

Any suggestions? With my first he breastfed until 18months and he stopped on his own. He's almost 9 years old.

It is really bad if I continue to breastfeed while pregnant?

Thank you for helping