Pregnant & Breastfeeding 💪🏼

DEE💋
At my first prenatal appointment, I was seen by a nurse practitioner who advised me to stop breastfeeding at 4 months.  She said that after that, it would be difficult for me to nourish myself, a growing fetus, & my 9-month-old.
At my most recent prenatal appointment, my regular OB said that at 12 weeks, we were clear of any risk of a miscarriage caused by competition in progesterone between pregnancy & breastfeeding.  BUT he said to stop breastfeeding by the third trimester at the latest to avoid pre-term labor.
Either way, I am being advised to stop breastfeeding.  I do plan on attending a La Leche League meeting next month to consult with lactation specialists to get a second opinion.
Are there any other pregnant ladies out there who are also breastfeeding?  Are there any mamas who have done it — successfully or unsuccessfully?  Or does anyone have any tips / advice to offer?  Any little bit of information helps, so thank you! 😘