I feel for you bro. Interviews are the worst. Have you considered online jobs? You mentioned that you're a graphic designer and I know a ton of graphic designers who work online from home. I work as a full time programmer but whenever I need that extra money I do some freelancing. There are sites like odesk, freelancer etc. Maybe you should check them out. You do have to pass a test and there is a sort of "interview" so that your client can know you better but it is over Skype and you can always type things out if you get really stuck(I do that myself). You can also tell them beforehand that you have a speech impediment and trust me many(if not all) won't even mind. They seek skill and if you're skilled enough(which I'm sure you are) you wont have any problem whatsoever. Good luck brother.