Atomoxetine's effect size is surprisingly similar to methylphenidate, though in my experience it treats different aspects of ADHD than stimulants. Some doctors (mine) are open to combining it with a long-acting stimulant, which actually can be a really nice setup, especially if you're sensitive to stimulants.

Hope you get it worked out OP. I will say, if it's ADHD, it's 100% worth trying to get the best treatment you can.