If you both aren't ready, I'd seek a second opinion. You can call the Australian Breastfeeding Association on 1800 686 268. See what they say! I know alot of toddlers tend to wean naturally once the milk changes to colostrum too
My son is too and I’m 30 weeks pregnant and still breastfeeding. I haven’t encountered any problems yet.. not a medical background here but maybe get a second opinion. Ask your midwives, because most of the advice is that unless you are a high-risk pregnancy, you can continue breastfeeding.
My daughter was 19 months when I fell pregnant and we were still comfort feeding. She weaned herself when I was about 20 weeks. Apparently the taste of milk changes while pregnant
I obviously don’t know your circumstances, but I’m finding it hard to think of any medical reasons why you should avoid tandem feeding.. GP’s are generally not very educated about breastfeeding, so you might want to look into some other resources.. if you still want to wean you can have a look on the Australian breastfeeding associations website. I breastfed through my 2nd and 3rd pregnancy and tandem fed for a few months after. I’m happy answer any questions