you are feeling typical mom feelings, and you are not alone.
im sure that omar is not the perfect little angel all the time, and even if he is, he wont stay that way every single month the rest of his childhood. every kid has a different temperment, and yours is just different from your sister in laws.
some kids, like yours and like mine, will just accept NO SUBSTITUTES for what they need or want. i call that determination, headstrong, and very motivated. these are GOOD traits that will serve her well as she grows up. in the meantime, it seems more like stubbornness, crankiness, and constant fussiness.
the first thing that struck me is that though you have an honest love and need to fulfill your daughters needs whatever they are, you yourself is frustrated. the question is less about how to get your daughter to stop crying and how you can feel better about the whole situation, and get it under control.
its very possible that you have a slight form of postpartum depression. dont worry, its common (more common than you think) and its very treatable and manageable. i wouldnt assume that you would even need drugs to manage it, because you arent feeling resent toward your child, but more a frustration that you feel so bad about not knowing what she wants. make an appointment with your doctor, even if its just your OBGYN. they will know what to do, and what to ask, and what the situation is if it is really postpartum. it could be just overwhelming exhaustion or something.
so please, talk to your doctor, and if you dont get a response that you feel comfortable with, see another doctor. sometimes a second opinion is always a good idea. have patience with yourself, and know that sometimes you just need to take a break. see if you have someone who will just let you have a whole entire day to yourself. if you are nursing just pump for a couple days one extra time a day, and you will build up a supply if you havent already, and that will hold her for the day. formula - no problem.
give yourself a break. dont try to make the house spotless. the sooner you give up on trying to clean the house, the easier life will be. i heard a quote somewhere that cleaning the house while your children are still growing is like shoveling the walk while its still snowing, and its SO TRUE. the minute you have one thing cleaned, something makes it dirty again. there is no one on the face of the earth that can have every dish clean in the house at one time, or every floor clean, or whatever. its just not possible. so cut youself some slack. its amazing sometimes to look and see the mess i allow in my house since i had my son. i would have freaked before he came along, and now its just like, i would rather spend time with him or something, than clean the floor every single day. you know??
please write to me if you just want to talk. it also sounds like you are pretty lonely - do you have any close friends who you can spend some time with? its important to have someone to talk to, and sometimes husbands cant fill every single need we have as women, and thats ok, it doesnt mean our marriages are bad, it just means that its normal. our lives cannot possible be totally fulfilled by husbands and children; we are just not meant to live like that. i myself have often been frustrated just thinking that i really dont have a close friend i can talk to. i have a handful of really good friends, but they just arent at the same place in their lives as me (dont have kids) or do have kids, but things just dont work out you know ?
so anyway. take a break. see if once a week, you can find someone to babysit her for a while, and just take a walk or a drive or watch a movie or something. do something that recharges YOUR life. :) mine would be driving with the windows down and the music loud. it feels SO WIERD to not have my son in the backseat, talking away, but at the same time, it feels SO NICE. :)
oh yeah, and any stress you have is going to transfer over to your daughter, and its going to stress her out... so its possible that shes anxious because you are burnt out. its ok, its not your fault and you are not hurting her, shes just naturally and instinctivly worried. :) taking a break will help! :D
one more thing. i heard another quote somewhere and i printed it up on my computer in fancy letters and posted it in my kitchen where i would see it every day, and i also printed it up for my other mom friends.
the quote is this:
remind yourself every day "what my child needs most is a happy mother"
and make sure that you do something for you once in a while, if that means taking an entire nap break on the computer, or painting your toenails once a week, or going to get a massage once a month, or just taking a walk, or drive, whatever. :)
anyway,
good luck