I saw already tutorials on how to create camo fondant, with little pieces of colors.  My question is, can I cover the cake with the camo fondant or do I have to cover it in regular fondant and then the camo one just in case the pieces separate?

It seems like you could roll out a piece of solid colored fondant (a shade of green). Then apply Yor camo technique by adding small pieces of colored fondant and using a rolling pin to roll them into the bottom, solid piece.  I think it will all become one solid sheet of camo fondant that can be applied to the cake. 

I tried the technique of the small pieces of colors rolled together to get the camo look & it looked great until I applied it to the cake.  I found that it pulled apart in several spots.  I didn't put a layer of fondant under it though so maybe that would help?

yes, you'll only need to roll out the one piece.  group all your balls and "L" shaped fondant together in random patterns, (mine were about 1cm thick before I started rolling). when satisfied, start rolling it out.  it will all blend together as one, if it's not big enough to cover the cake, add more balls and L shapes to the outer edges and roll out some more.  I then roll it up on my mat and drape it over the cake.   i layed this right over my buttercream with no problems

Thanks!

what I'm scared is once I put the camo fondant on the cake, the little pieces will separated and pull apart in some spots, I don't know if what I say make sense, please anybody tell me that understand me :(

lol..  I understand..  that's why I make my clumps a little thicker.  So when rolled, it blends together enough that there are no seams between the colours.  If you can, after you roll it, you could flip the sheet and do another roll on the backside.. just to make sure it's fully blended?  

I will, thanks!