Need help with Ab Training

I'm training my abs to improve my form on circles, but whenever I train, it seems that my right side of my abs are being trained more than my left side. I know that the body proportions are different for most of us, but I seriously don't like it.

Also, do you have any suggestions for training the obliques effectively? I tried oblique crunches and holding a side plank, but I don't feel any difference on my left oblique.

I seriosly doubt there is a problem in your abs, it's much more likely wrong or bad tecnique.

Again, most people are slightly stronger more on one side than the other.