I have spent the better part of a week planning my cake, it seems however the cake didn't rise as much as I expected.

I used two packet cake mixes to make a rectangle slab cake, but it has risen a lot on the middle and is very small at the sides. I don't think I used enough cake mix.

Do I just go with it as is? It's hilly to say the least , lol atleast it will suit the racetrack theme
But it certainly didn't go to plan, should just ice it and be done with it?

I don't even know for sure what went wrong help?