I assume you're playing Gen V since you're trying to find a Shiny Pidove.
The probability of finding a shiny is 1 in 8,192.
In Maths, it really just means that in every eight thousand Pokemon you find there will be at least one shiny.
Just keep trying, I guess is the only advice I could give.
If you want a Shiny Pidove you could try using the Masuda Method, where you can breed two Pokemon as usual (like, both male and female, same egg group, etc.) but the two Pokemon are from different countries.
E.g., you can breed a Japanese Male Hoothoot and an English Female Pidove, and the egg has six times the chance of being shiny. (6 in 8,192! or about 1 in 1,365)
So you can always try continuously breeding if you want to increase the chances.
Hope I helped. :)