Tips to get baby to stop breastfeeding?

C

Hi all, i started weaning my son at 12 months. He’s now 18 months and I’m 14 weeks pregnant and still every morning when i come downstairs he literally lifts my shirt and pulls down my bra for milk. I honestly don’t even think i have any left!! Also, sometimes when he can’t sleep he does this also for comfort. How do i gently stop this? I don’t want to break his heart , but i definitely want to be done before the new baby arrives. The pediatrician told me to make sure I’m done by may Bc at his age if he goes 3 months without it he will forget and won’t be upset when he sees me feeding the new baby. Help !!