Firstly, congratulations to you and your partner on your forthcoming marriage, I hope that you will both be really really happy for many many years to come.
Secondly, you can wear absolutely anything you like to your own wedding, it is your special day. What I would say though,is don't close your mind to a more traditional gown, if you haven't already, please make an appointment at a local, but not 'designer' wedding gown shop, and go and be spoilt, go with someone you trust, try a variety of gowns, explain that you don't want a traditional, formal gown, that you don't necessarily want white or ivory, and let THEM find gowns for you, try them on and get ideas. You don't need to buy, but you will be able to make an informed choice.
If you walk away, and still want the dress you have chosen, then it is DEFINITELY your dress. But, you may find that in fact you DO want a more traditional gown, in which case you will have no regrets. The worst th I g would be to wear a non wedding dress and then look back at the photos in 20'years time and regret that you missed out on that ' wedding dress' experience.
Finally, if you want a non traditional gown, it is always worth checking out high street shops, Monsoon, is a great place to start, or Debenhams (we picked up 4 bridesmaids dresses for a total of £40' in Debenhams). Or many of the catalogues have some lovely dresses.