I'm scared..

I babysit a little girl, and I dread her coming over. (Already let her parents know I am getting a job so I will not be watching her much longer) She is four months,teething, refusing to sleep.. and screams any time I put her down. I cant even take a shit without this baby howling.. I'm 16 weeks pregnant and scared. What if I feel the same about my little boy? I would never wanna feel that way about him.. I'm worried. What if I cant be a good mom to him? Any other moms experience this? Have any of you just not liked other peoples children and loved your own I'm just so worried.