Sometimes it takes a while...some people wait years.
Ive been flying 3 years and it took me a good year to be successful, 3 big interviews, bumped out of my first and then got through with the other 2.
Dont give up, see each interview as a lesson and enjoy them aswell, meet other candidates and stay in touch, trading info is priceless in this business. Lots of people said I couldnt do it, kids and shiftwork dont mix etc...but i did and i am and i love it.
Keep Trying!