pregnant and breastfeeding

Esmeralda
Hello all, 
My son is 1 year and 5 months and I am currently 10 weeks pregnant with twins. However I am still fully breastfeeding my son and I've tried to cut him off and it's so hard. Is anyone in the same boat as me?
What do u think of a mother who breastfeeding and pregnant same time? Is breastfeeding my son harmful to my unborn babies? 
I've heard from elders like my mum and others that it makes the other childten in the belly not grow properly or have problems
I am feeling both scared, worried same time don't kno what to think but I've tried to cut my son of breastfeeding so many times that it's become a constant battle and I feel distraught about it. Only way I can think of it working is if my son stays with grandparents for a week without me and that's not making me feel any better 
Any help and advice is welcomed