Hyperthyroid?

[Bumpk1n]

Cat is my boyfriends cat but I moved in with him recently. She's going to the vets on Saturday but just wanted some other opinions.
She hasn't had a check up in years, boyfriend couldn't drive so had no way of taking her to the vets, bit irresponsible IMO. He can now drive hence why we are going on Saturday.
She is a small tabby about 8 years old. However she seems to have dropped weight recently and her coat is looking dull, it didn't really have a nice shine even in the summer.
She is very timid! Almost to the point where you would think she's a rescued abused cat. She jumps at every noise, always appears to be on edge while she's awake, tail constantly flicking. To me she doesn't look like a happy cat.
She often eats grass and is then sick.
She's wormed regularly and eats lots of food, so I don't think she is wormy or malnourished. Boyfriend used to give her lots of dreamies but I stopped that.
Any ideas? Thanks :)

[Bumpk1n]

Should add, I've had cats all my life. Current cat still at my parents is going strong at 15 years old, looks and acts much younger. She is a very happy contented mog. Obviously I understand that all cats have different personalities but BF's cat is so jumpy and nervy. We tried a feliway but it made no difference