Stressed,

I'm 18 weeks with my second, my first is 14 months almost 15 months old and lately she hasn't been sleeping properly and waking up very early, I'm exhausted and I'm becoming stressed out thinking am I going to struggle even more when bib comes, my partners a working man and helps out as much as he can and let's me relax on Sundays witch is he's only day off but how have u second mummys been? Is it has hard as what I'm thinking its going to be, is my daughter going through a stage ?