This may sound like a childish question and for all its worth, very well may be one as I am only 17, but how do I know who to trust with reviewing or looking at my work? The idea of someone stealing someone else's work, sounds so horible I cant imagine anyone doing it, but I am still not very secure on the topic. So who should? and shouldn't I trust? to show work I have done to.
I also often don't know if work I have done is of any value, much of my work, may very well be crap. But if I ever have or create somthing of value, whom do I trust?
For better or worse, being unusually concerned about having one's precious ideas stolen is one of the classical hallmarks of a mathematical crank. Therefore if you get visibly protective, the loss of reputation you'll suffer simply because you sound like a crank is likely to outweigh, by far, the very minor risk that you lose the opportunity to earn some reputation because someone took one of your ideas and ran with it.
Part of the equation is that just about everyone who actually does new mathematics always seem to stress how much more productive it makes them to discuss their ideas with an audience. If you can find an audience who are capable enough to be able to make something with your ideas if they (hypothetically) did take them and run with them, chances are overwhelming that they will have too many ideas of their own to give all of them their due. But there's a good possibility that some of them would give you a few minutes of their time to ask the fortuitous question that pushes you in the direction of the eventual solution.
And even if your presentation inspires someone to do some real work on top of yours, it is overwhelmingly more likely that they'll suggest a collaboration than just appropriate your ideas as their own. Doing so is not only the right thing do do -- it is practically without cost to them, because being known as "Jones who published such and such" is not much more prestigious than being known "Jones, of Jones and Smith (who famously proved such-and-such)".
Also, if your ideas are that good, they'll want to stay friendly with you so you'll let them know about your next good idea and give them a chance to collaborate on that, too.