Oh Marianna, I'm sorry about this. Like Maya, I know this feeling very well. Job hunting can be exhausting, humiliating, self esteem-crushing, you name it. Before I moved to England I was like you- very confident, as I'd never NOT got a job I'd interviewed for. Now I'm well-versed in the old "the other candidates were more experienced" line, lol! I think it can actually be a good thing, as you learn not to take things personally (though it's tough, of course) and discover you're much stronger than you ever thought.
Keep in mind that in this climate (and yes, I hate people always saying that) even getting an internship can be tough. While five years ago a company might have been happy to take on an intelligent, eager-to-learn young person with whom the team got on well, things are different now. These days companies often look at interns as unpaid employees- ie, they want someone with a very specific skillset who can actually save them money. It's not a good thing at all, especially for people who want to learn the ropes of a specific business, but there you go.
It might be a blessing in disguise- these days, it's easy to fall into the "intern rut". I'm 25 years old and I know many people who are essentially "professional interns", ie. have been interning at various companies for years, thinking that it will land them a plush job "one day". Of course the fashion industry is notorious for this kind of treatment, far worse than most other businesses, but still- you don't want to be where they are, trust me.
So chin up! There is something better just around the corner for you, I know it!