Is this ok for a 3 week old?

Yasmin • I'm 21yrs old grown up with bad ibs which made me in constant pain growin up ended up with fibromyalgia 2 yrs ago and now I'm going to be a mum :)
My 3 week old had 3 floz during the day and maybe sometimes 4 floz but seems that at night he only want 1 floz, is this ok?