don't be worry...some of my friend's baby they getting thin while growing...especially during 6mths to 3yrs old. thats very normal and they'll become healthy, strong and even fat when they start to have exercise (like walking, running, jumping) of their own
ps. don't pushing yourself so hard, i understand there should be pressure but pls don't be..just make sure your baby sleep well, pooh well, eat well and mentally happy. because your negative feeling or motion will transmit to your baby