9 month old nursling and 6 months pregnant... supply?!

Hi ladies!

As the title says, I am 6 months pregnant with a 9 month old nursling.  It's hard because I am having trouble finding support from my sons pedi and my husband doesn't feel like the advice from my LC is accurate and insists that I supplement.  I can feel my supply is lower but it's so hard knowing how much milk he needs.

Any suggestions?