Why do my RAW to JPEG conversions look darker?

Ok, they don't "look" darker, they are! Putting my 2 images side by side, the raw file that i edit to my wants looks perfect, when i save it as a jpeg and open it, it comes out considerably darker and less "smooth" (looks more rough-ish). Why does this happen? I'm new to this dslr stuff but i don't get why my images come out with less quality, it's very frustrating! I take pictures of food for a blog i'm starting and i want my images to be unchanged when i post them but the jpeg looks worse in quality. Is there any way i can keep the quality i see in raw after it gets converted? Should i just shoot in JPEG as opposed to RAW if converting is going to undo my editing anyways? Some help would be greatly appreciated.

also, just in case, i have a nikon d3100 and i edit my raw files in adobe photoshop cs6.

RAW images are unprocessed - you have to process them yourself - you will have to tweak the exposure yourself, and you will have to add noise reduction yourself.

Jpegs out of your camera are processed by the software in the camera, that includes adding noise reduction, increasing contrast/saturation or even adding sharpening.

By the way, when you process RAWs in Photoshop - you are not actually editing the RAW, you are processing it. RAWs can't actually be physically edited without first converting to another image format.