My sweet cat suddenly became very aggressive

[Linguini1]

Hello and thank in advance.

I have a 1 1/2 yr old Cat that is the most amazing cat one could have. She is spay and her annual shoots. The Vets are even impressed at her behavior. She is on a grain free diet Blue Buffalo/Wellness She welcomes strangers, lies on my chest and begs to be picked up however suddenly she has gotten extremely aggressive. It started in the morning after getting out of the shower she wants to be picked up and I do so I give her many kisses and she loves it but as I was holding her she jumped off for no apparent reason and started hissing and growling which I haven't heard her do EVER! I left for work 9 hours later I came home to hold and feed her the same thing occurred only this times she became really nasty wanting to scratch, hissing lunging at me and growling really loud she seems to have no signs of pain. so i invited a friend over to see if she would react to same way and she hasn't. I am bewildered as to why suddenly shes become so aggressive towards just me. i eve took a shower after getting home thinking that maybe it could be a scent she didn't like but the problem persisted. i'm really nervous my cat is my life and the thing that loves me unconditionally. What should I do? could it be a urinary tract infection something inside?  

[Linguini1]

Thanks guys for your help she had a pain in the middle of her back the vet gave me pain meds and she got a pain shot. I think she may have pulled her back from jumping on my computer chair that swivels to get to her window perch

[hhall323]

I know you said she has no signs of pain but maybe just certain spot that hurts only when you pick her up. I watched a show about cat behavior and the cat was fine until the person touched a sore spot on him. Maybe just let your cat do what she wants with you, rub her on the ground and watch for a certain place she doesnt like to be touched. I hope things get better for you

[margypops]

I wonder if she doesnt like being picked up how do you do it, sometimes it can hurt, try petting her whilst she is on the ground or a chair...pain will make animals aggressive .My cat hates being picked up so I stroke her when she is on the ground or where she is sitting ...