Breastfeeding my newborn and starting again with my 1 year old???

Ca
Ok im a new mommy to a almost 8 month old...and im also 13 weeks pregnant with baby #2.(yes we were trying ive lost multiple babies and want a big family)anyways...i breast fed my 1st for about 2 or 3 months and i had a low supply and decided that he wasnt getting enough from me, im really wanting to breast feed my 2nd and possibly have ( then will be a little over a year old) my first son to breast feed again...he has 4 teeth already and likes to nibble, has anyone managed to be successful at this?? I still had milk from him when i was pregnant the last time but they said not to continue to breast feed while i was pregnant....so im dried up now.how can i transition him back???