I know how difficult it is to have a sick little child. My own daughter was very ill as an infant and toddler, and had significant eating and sleeping problems.
It's easy, and natural, to say that your child has been sick a thousand times, and refuses to eat, when you're exhausted and discouraged. I know how tired you are. When asked "did she sleep" the answer in your foggy brain comes out "no, she hasn't slept since 1995 and she just had her 2,000th strep throat infection". Of course, that's an exaggeration, but when you're that tired, that sounds about right. I get it.
But when you're seeking help, you're going to need to be more specific. "Sick" can mean so many things - diagnosed tonsillitis, a fever, being listless, vomiting, being cranky, etc. And "refusing to eat" can mean literally turning down food, or being very picky.
I suggest you get her records, as others have suggested, and organize them into a folder. Organize them chronologically, and highlight the important parts (date, diagnosis, medication prescribed).
Then get a notebook and begin your own journal. Keep a record of every day on a new page. Note sleep/wake times, food eaten and when, liquids consumed. Be specific. Don't write "drank a little"; write "drank half a sippy cup of milk (and then figure out how much one sippy cup holds); "ate one slice of American cheese" etc.
Video her on your phone or camera. If she's babbling, or if she's not uttering any sounds when you talk with her, video that. If she is trying to stand and walk but stumbles and falls, then video that. If she can't pull herself up to a standing position and won't take any steps (even towards a toy), then video that. Note the date and time.
All of this info will be helpful both to you and to a doctor and/or therapist. This will give you a clearer picture of what "a thousand times" really means, and what "refused to eat and drink and sleep" really means, in concrete terms.
Most importantly, don't lose hope. There are specialists that we non-medical people don't even know about. Sleep deprivation and insufficient nutrition can affect a child greatly. There are sleep studies that can be done, and pain specialists, and neurologists, in the event that your daughter needs that. There are occupational therapists (which has nothing to do with occupations - it's help with finger control, walking, etc), physical therapists, early intervention specialists of all kinds.
But before you can really get the help of any of these specialists, you are going to need careful, non-emotional, documented, daily specifics of your child's behaviors, and you're going to need organized records.
Just start by getting all her records, and start with a journal of her daily activities. And NEVER lose hope.