Almost 2 year old cat with possible thyroid?

So my female 1 and a half year old cat has always been skinny her whole life. She's so hyper , vocal, and friendly to everyone which I thought was normal. And at around 7-8 months she became pregnant and beared only one kitten who is healthy. Her growth became stunted and has been the same size ever since. I am only now noticing how hungry she always is and how she never gains weight from eating both dry and wet food. For the past 4 months about she has been vomiting every so often and now she's starting to pee in random places besides her litter box. After looking up symptoms of thyroid it scared me because she matches every one of them. The only thing is I've read thyroid usually only occurs in older cats. Can my cat really have a type of thyroid? Is there any possibility it is not that and something to do with her giving birth so young? I have two other cats that are healthy and she has always been the odd one out with being so hyper all the time. I am really scared but will end up taking her to the vet this week to find out for sure. Please let me know if anyone has had This type of experience or knows anything about this thank you

You should definitely take her to the vet to get checked out.  She is very young to be hyperthyroid, but there are other conditions that can cause a high metabolism.  As for peeing in various places around the house, she may have  a urinary infection or just urinary irritation.  You said you feed her wet and dry food, but it's important to know WHAT is in the wet food and WHAT is in the dry food you feed her.  Is she getting good MEAT (not plant) protein, moderate fat, and LOW carbohydrates?   So many of the common supermarket foods today are not appropriate for cats, who should not be eating corn and wheat and soy or peas and potatoes.  Your vet can check her for worms and make sure she is vaccinated against illness, and if she is not yet spayed, it's time to do that also  She will be much happier.  She sounds like a wonderful cat and with proper care she should live to a ripe old age.  Here is a list of the worst dry foods to feed, and inside this list is a list of the BEST ones.  Of these 7 common cat foods, only ONE of them contains actual MEAT as the first ingredient.

http://petslady.com/articles/worst_foods_you_can_feed_your_cat