Viewing 13 as a bad number is a superstition, to most people, so don't just jump to conclusions based off of a belief.
Magick takes time, and you will know when your spell was successful when your results manifest in some way. Worrying about it won't help, as it will begin to make you have doubt as to wether it actually worked or not. Until you see the change actually happening, don't stress about it. Sometimes people just want everything to be a 'sign', and most of the time that is not the case. Just ignore it and wait patiently, and everything should come out just dandy, especially if you did the spell right :)
Good luck and blessed be.