Is it supposed to be this HARD?

Is being a mom supposed to be this hard?  Its 8:30 on a Sunday night and my husband left me home alone with the girls to go hang out with a friend.  When he left the youngest was asleep and our oldest, as is her nightly ritual, she was tucked in in her bed reading to her doll babies until she falls asleep.  I am sitting here trying to have the only alone time I get all day.  This is the time of the day that I exercise  (when I can make myself do it, not tonight), I try to read my bible (this is what I was in the middle of doing), I do my daily devotional, and then maybe read a book before bed.  This should have been a piece of cake for a "veteran" mom like myself.
Maybe 20 minutes after he left my 1 year old starts screaming.  For a little while now when she wakes up or is trying to go to sleep she screams like she is in physical pain it is excruciating.  Also last night she was up every hour or two all night.  As I am trying to go get her my 3 year old, who is not supposed to be getting up again, comes walking out of her door.  She wants a different book in her bed.  I tell her its too late to go back to bed.  I pick up my youngest and take her to rock her back to sleep.  My  oldest come back out asking for the book waking her sister back up and this time I yell at her.  She runs back in her room slams the door and proceeds to scream. I get her sister to sleep then I lay her down in her crib and she starts screaming again.  (We have tried to just lay her down and let her scream but 30 minutes later when she was not even letting up we gave up.)  I got her to sleep two or three more times for her to wake up just as I am leaving the rom and for her to scream again.  In a last attempt I am rocking her in a chair in her room.  She is just laying there one hand clutching on to my shirt for dear life and I'm crying.
I don't know what to do.  For days now she has been irritable, nothing serious but this screaming at night and just being extra clingy.  I don't know if there is something wrong with her, or is she going through a phase, or is she just having a bad couple of days.  I have already asked my husband if he thought that we should run her by the pediatrician just for a check and the only response I can get as usual is "I don't know".  Responses like that and the expectations that I feel like that puts on me is such a heavy weight.  I'm the mom so I am supposed to know.  But I'm also the one that has to deal with the crazy looks when I take her to the dr. and can't tell them whats wrong it just doesn't feel right.  On the other hand when my chid never cried but had a double ear infection I was the one that got those looks when I finally took her in that day too.  The I thought about how I have an 8 o'clock appointment in the morning, but my husband is pulling double football duty for morning and afternoons this week so that leaves me to try and squeeze in her appointment, if i decide to take her.  Also I have to figure out how to pay for my appointment and if I take her we have a huge balance at the pediatricians right now.  How much of me that I don't have to give will they want too.
I'm trying to be a better person and to lean on God in moments like this, but its so hard.  And you just feel like if you can't do any of this right do you even deserve His strength.  I know deep down that I do, but in these moments all I can really do is ask- Is it really supposed to be this hard?