1998 Honda Accord More travel in the brakes

Do you have four wheel disc? Or drums in the back? If you have drums, try pulling up on the parking brake, if the pedal is good now, you need rear brakes. If the pedal remains low, you need hydralic parts. If you have disc brakes, you should ckeck the pads, replace what is needed, and before you push the pistons back in, look inside the dust boots for leaks, rplace any leaking part. If the caliper on one side is leaking, replace both sides!

I actually just got my calipers replaced (after there was a squeaking sound) about a month ago, and the travel of teh pedal decreased and everything was normal. But now, a month later, the same problem has returned except there is no noise this time.

Tell me exactly what parts, front and back have been done...

just the calipers were replaced on the front wheels. Back wheels' bearings were replaced about a year ago. The problem is that I have to press a bit more on the brake pedal for the initial slow down but the car stops fine.

Try pulling up on the parking brake handle with the release button pressd and see if the pedal feels better. Get back with the results.