Weaning toddler while pregnant

My son is having a very hard time weaning and has gotten very insecure. I wasn’t planning on weaning him but with this pregnancy I can not afford to lose the energy from it. I work part time in the morning and my husband is away at school and only comes home on the weekends (weather depending) so my son has a lot going on that makes him insecure and I’ve had to stop with the daytime breastfeeding because of the energy strain and I need to know what else I can do to help him feel secure. He just sat and sobbed for 20 minutes straight because he always would breastfeed after a nap and he wasn’t allowed to yesterday and today and it’s taking a toll on him and I feel guilty but I don’t know how to fix it