Hi S.,
It is frustrating when the pediatrician does not listen to you or they act like you are crazy! You do need to listen to your mommy voice. If you think something is wrong, and you have really checked out all the possiblities for more common things, then go back and ask again, or find a pediatrician who listens to you.
From a seasoned Mom, she may have a cold that is unrealted to the problem you think of as possible reflux. Colds in newborns are often mild and last longer than in older children and adults and they may eat less. As long as she is not dehydrated and she continues to gain weight, they will probably wait out a cold.
A gassy newborn is not going to gain much attention from the doctor because this is so common. Try symethicone drops (these are safe, inert-which means that they are not absorbed by the body) and are effective at releiving gas which could be totally unrelated to anything else.
Constipation is a problem only if the stool is hard, or if the stool is hard and they are not going at all and strain to do so with out result, not if they are just not pooping as much as they used to. A babies gastric system is immature at birth and is going through many changes, and this could just be part of the maturation process; her stools will change dramatically over the next year (trust me) and every change is not cause for concern. One Tbs corn syrup in one cup of boild water (cooled) will ease mild new born consitpation if you really think she is in distress about it, I don't recomend it if you are in distress about it though, so don't give her this unless she has hard stools and is un comfortable. Glysserin suppositories (sold over the counter at your pharmacy for new borns are also an alternative and they work!)
If you can exculsiviely breast feed, I would try if that is how she seems most comfortable, and you might consider that the formula is not right for her too, maybe she would tolerate something else better, if enfamil was reccommended by her pediatrician, speak to them before you try something new or ask what they suggest for her issues. If she is gaining well, then you know you are doing something right, and this will probably always be the doctors first question.
I have never had a child with reflux, but I think that they spit up a great deal, so maybe her issue is something, but you are not describing what they usully see as "reflux" and they are writing you off, especially since you have many common complaints that they hear from many Mom's of newborns. I would gess that if you are adding them all together when you tell them about her issues, they are not hearing the one thing that you see that is long term and might need more attention, which is the whole thing you think is reflux-try not using a lable, and nix all the other symptoms in relation to this, and see if you get an answer you feel better about.
She may also may be entering a colic phase. What you describe is happening with a specfic pattern, night time discomfort, it can start every day at 5 or 10 or even in the morning. Some babies are uncomforatble through the third month and beyond. One of mine was like this, and like magic, as she turned three months and it was over. You never know.
The pediatrician is going to be looking for weight gain and specific things that tell him that it is NOT one of the more common baby discomforts. I hope some of these things work out to help you ease the common stuff so that you can single out anything that needs the pediatricians attention.
Good luck honey! You are doing fine, as long as she is gaining weight, she is probably going to be fine. Even if it turns out that something is wrong, you will make it through and you are doing a good job. Relax, sleep as much as you can, and know that happier baby days are ahead!
M.