Thanks.
First, I'd need to know what team you're using. You maybe should be handling teams fairly easy.
Secondly, the only advice I can give to make the game play harder is to tweak some sliders, depending on what you do well against other teams. If the run game is too easy, adjust the user Run Blocking slider down a bit, until you see a change. Doing too well in the passing game, adjust the CPU Pass Coverage slider up a bit. Not throwing INTs, go up a bit on the Interception slider. The Reaction Time slider should result in more defensive pass break-ups and INTs as well, as DBs will break on the ball quicker when you throw it. The list goes on and on with slider tweaks. Just don't get too lost in too much tweaking or you'll get the worse thing in Madden slider-adjusting, "slideritis." Where it seems to never stop.. lol..
If it is too easy though, there is always Charter's All-Madden sliders. I'm sure they are pretty good.
My best advice though, is to figure out what your strengths are, think about what slider might need tweaking in regard to that, and slightly tweak them up or down. I usually use increments of 5 when adjusting, but 2 or 3 can work fine as well.
Anyway, I hope you can find a better balance if the game is too easy for you with these sliders. You can always try other All-Pro sliders, All-Madden, or do some tweaking of your own, which I always encourage to users.