You had difficulty gaining levels? We must have been playing different games then. I seem to remember being over-powered very early on. Heck. I oftentimes was able to wear Power Armor and use a Gauss Rifle before even killing the Rat God.
So as I said before. If you don't like it, don't download the DLC, easy as that. Or just grin and bear it. It's happening regardless, and not wholly unwelcomed. And these five levels don't make you even close to as overpowered as you could have been in both Fallout 2 OR Fallout 3.
Did you play fallout 2? And if so, did you EVER get over level 27 or 28 before the end of the game? Level caps don't mean that much when the exponentially increasing requirements make it virtually impossible to go past a certain level.
You really had to do pretty much everything in order to get the level 24 perk of sniper or slayer much before you finished the game.