Duck not eating :( .... Please help!

[FluffyDucky123]

So I have this Pekin duck about 2 months old. (I haven't sexed it yet guessing it's a she) (btw, how do you sex a Pekin duck?). She was fine until one afternoon when I went to check on them. I saw her laying in a corner and when I offered them food, she didn't want any (which was unusual). She would refuse all food offers and just sit down the whole time. The next morning, I went to check on her, she was a little bit better... but when I took her out to the grassy area, she started throwing up and shaking her head. A piece of wood chip came out, but then she continued throwing up and shaking her head like something else was in there as well. I haven't fed her anything weird... it was her usual diet. After all that throwing up she started drinking water like crazy (and that's the only thing she would eat/drink). She also seems really tired and sits down. Plus, she doesn't chirp anymore. Please help! Idk if she's laying eggs or not... but would laying eggs make your duck lose its appetite? Thank you!
Also... she just pooped and her poop is white and watery with a little bit of green in it. I'll try to send a pic.

 

[nuthatched]

She's too young to lay eggs if it is a she.
What's her diet? She must have had a wood chip stuck in her crop, can you feel her crop to see if there are more.

 

[FluffyDucky123]

For her diet, I usually feed her duck feed from Manna Pro with some vegetables. Water is always available, and sometimes I give her a little bit of fruit. I felt her crop, but she had so many feathers I couldn't tell properly. It doesn't seem like there is something there, though, however, every time i touch her head, she ducks in a weird way. Does she have a sore throat? Today, she ate a few lettuce pieces with was good
Btw, now she poops water?? Its all clear liquid