Doubting Thomas

Sometimes ... No.  Many times, I come to work and wonder how I made it here.  I wonder how my mom worked full-time while I was an infant/toddler and wonder how my boss had 3 kids and is a professional powerhouse.  A lot of days I don't know that I'm cut out for it.  Seems to me that motherhood brings along with it a whole lot of self-doubt - I'm constantly doubting myself in areas I was previously confident in or, if not confident, I didn't give it much thought and just did or decided whatever. 
Last night, Urban Cowbaby seemed to be having some tummy problems - I think his tummy was hurting him but we haven't taught him the sign for ouch yet (haven't had much need for it) so he couldn't tell us what was wrong.  So, we were up with him more of the night than we were sleeping and it, of course, is tiring.  Now, Urban Cowboy and I are no strangers to sleep deprivation since the advent of the little man - he didn't sleep through the night until after he was 1 year old - but, lately, we've been accoustomed to getting a good night's sleep and last night ended up being a bit rough on us.  We weren't nice to each other, we were not being positive; we were being tired and cranky and wishing we were someplace else and that Urban Cowbaby wasn't crying and clearly uncomfortable. 
And the tiredness and self-doubt make me question whether or not it's worth it to drag myself to work 3 days a week (I know, it's only 3 days!) because I am definitely not giving 100% to my job ... is that fair to my employer, my team, myself?  What will I think of current self  60 years from now when I'm in my old age and reflecting on my life?  Will I think I have made the right decisions?