Im Breastfeeding A 5 Week Old Baby…!?

so iv been exclusively breastfeeding my 5 week old son. my breast use to feel full, and wold leak a lot.
i recently noticed about a day ago that my breast are back to my pre pregnancy size, and soft. and this morning he was fussy while he ate. idk if this is normal. is my milk drying up? :/ i am fearing that this is happening…
i have a pump , but a LC told me not to pump untill my son is 6 weeks and we have established a milk supply.
was i suppose to pump before 6 weeks, ? did this happen to you? what can i do to increase my milk supply.? i really dont want to feed him formula.
he does pee , and poops he does but sometimes a little sometimes a lot he does burp and this morning he spit up a little.

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