Cat has suddenly started to bite me

Question
We have a 3 or 4 year old siamese and in the past few months, when I have attempted to pet her, she bares her teeth and tonight she bit me with the two long teeth to the point where
she drew blood.  
I find this strange as I have never been bitten by a cat before,
she accidentally scratched me a week or so ago, and I know that part of that was my own fault.  But the marks on my arm are both from her left and right long teeth.
Should I stop trying to hold her and just use toys, from what I have already read, it seems that cats really don't like their
people to play with them physically.  She sleeps with me every night but I just would like to know if I should stop trying to pet her as I have done in the past when we had dogs.

Thank YOU

Answer
Mary,

Is she spayed?

Assuming she is spayed, if this is a sudden change in behavior, there might be a medical issue.  I am also assuming you have had this cat for quite a while, and she used to be more tolerant of being held and petted. Again, a sudden change in behavior may be due to a medical issue whereas your holding her or petting her may be causing her discomfort. If this is the case, a visit to the vet is warranted. If you see the vet also have the vet check the thyroid levels as this can also cause changes in behavior.

It is difficult from your question to ascertain how long you have had this cat.

Can you clarify the situation, please?

I look forward to hearing back from you.

Best regards... Norm.