Watery poop. This? how this will change?

My son is 1month 8days old.He is not full term 37wks 2days birth weight 2kg760gm.After 27days,his weight was 3kg400gm.Since the beginning he passes stool everyday many times.Sometimes yellow seedy,sometimes full watery..is this yellow watery stool normal?is it dehydration?what should I do to stop this?He passes this watery bubble stool instantly after every feed and he tries very hard to pass stool and gas,he grunts before passing gas..he is on breastfeeding..most of the time, he sleeps after 5minutes of sucking in my lap,I tried every possible way to wake him but in vain.then I put him on bed,within 30minutes he wakes and cries and again I feed him..how this will change?he pees after every feed ..pee count more than 6times..he can sleep whole night in my lap,but not in bed..I'm feeling completely restless and helpless.