First, "knowing you have now" would include knowledge of how much better life would be if you could only brush your teeth, get rid of the bugs crawling all over you, and being able to find a good conversation. Also, you would have memories of warm, dry housing, light at night, and entertainment. So, even though everyone around you would be fine with their world, you'd be constantly miserable.

Worse, all your knowledge, such as how to purchase good electronics, how to cook using just a microwave, and how price fluctuates with demand wouldn't impress anyone. The locals would probably have extensive knowledge of food sources and gathering techniques, as well as predator evasion, and would think you pretty stupid for not knowing those things. Likely, they would let you get eaten. Also, none of the women would actually look like Barbara Bach or Raquel Welch did in the movies.

You would starve to death because you would not have the skills required to capture and prepare your food. Virtually no one living in the United States would have sufficient knowledge of the skills required to live in such an environment.

This question reminds me of a movie, and I'm not sure which one it is... there's a time machine, and they tell the guy don't touch anything! Don't even step on a bug! So he goes back in time, steps on a butterfly, goes back to the future, and everything's different... all because of the chain reaction of stepping on that butterfly way back when.

But regardless... what it'd be like... well I'd feel awful smart and powerful. I'd know more than anyone, I'd be able to teach them all sorts of things that they'd think were magic. They'd probably think I were a goddess, so I'd get special treatment and they'd worship me. Well, either that or they'd get scared and think I was a demon and then they'd kill me.

I'd imagine it would be frustrating and scary too, though. What would happen when I got a cavity? There's no dentists. What about an infection easily cured by antibiotics? There's no doctors. What about childbirth if I ever wanted a family? I'd imagine that would be much more risky. There would be so much death and suffering all around me that I would feel like I should be able to control, but it wouldn't be in my power to do so.

So it would have its pros and cons, I think. Mostly depending on if they decided to call me a goddess or a demon, though. ;)

Your conceptual knowledge would be incredibly more than anyone in the stone age making you the smartest, and thereby easily allowing you to rule over them as a "god". While you probably can't apply any of that knowledge due to a lack of infrastructure (all our assembly lines and stuff making the technology we use everyday), you surely won't have a problem living since you'd be ruling over all of them; they would be the ones you direct to get food for you. As you tell them to do it, you can observe them and learn for yourself how to gather food if by some random chance they decide to overthrow you =)

We cannot travel in time because our bodies cannot handle it for example you forward in time and you get older go back and you get younger.