as a Lactation Consultant I can tell you that if your son has normal stooling pattern (that is the number and volume of poops has not changed dramatically) and has normal urination (the number and color of pees has not changed dramatically) then he is probably just fine.
Babies often develop some greenish color to their stools when they have slight gut irritation. This can be a mild reaction to something in your diet; a reaction to teething (possibly from swallowing excess saliva); an overload of lactose (milk sugar, usually from not draining the first breast well before changing, or when mom has way too much milk); a mild gastric bug; or other reasons.
It is not significant unless baby is distressed; true diarrhea is present with the risk of dehydration; there is significant amounts of mucus in the stool (small amounts or some stinginess is normal); there is noticeably blood in the stool (don't go looking for it but if you see streaks of blood then call baby's physician); or baby is not growing and developing well.
By the sound of it you are not in any of the above categories of concern that would require closer evaluation. The only thing you mentioned of concern was 4 wet diapers a day. I would expect him to have at least 6 to 8 pees every 24 hours. If the wet diapers are very wet then that may be fine and you did indicate he may be having more. If you are fortunate enough to see him pee outside a diaper then you will be able to check he has a good stream of clear, almost colorless to pale yellow urine and will know he is well hydrated.
In the mean time - greenish is ok as long as the baby is otherwise ok. This is a very common concern particularly for first time moms.
If you want to talk with a lactation consultant then you can find one through the listing at www.ilca.org. Most of us are happy to provide some free reassurance and counseling over the phone and will be able to ask some more questions to determine if further evaluation is needed.
As an ex ped ER nurse - follow your gut feeling (I mean true gut feeling not general worry or concern) - if you truly believe something isn't right with your baby then act on it an insist on a full evaluation. You know your baby better then anyone else.