My toddler is not eating much, what can I do?

My 19 month old daughter is really going off all foods. Every time it's food time she says " I don't want it". She says this to everything now. She will eat fruits, nuts and other little things but she won't ever eat when it's dinner, breakfast etc.

I'm getting worried she hasn't gained no weight in 3 months, she's stayed the same. She's a little chunky anyways but surely she should put on weight!

I don't know why she isn't eating, she has 16 teeth and no sign of anymore coming through now. She never says she's hungry any more. She always use to say 'mummy I'm hungry, yum yums'. Now it's like a terrible time for her ah!