The trackpad should not need heavy pressure to work (although heavy is obviously subjective.)
Did the amount of pressure required to create a click increase? If so, this can sometimes indicate that the battery may be pillowing (and it will need to be serviced if this is the case.) Additionally, IIRC there is an adjustment screw in the trackpad assembly that sometimes needs to be adjusted (someone smarter than me will verify.) Further, sometimes gunk can accumulate in between the edges between the glass trackpad and aluminum unibody frame, and this can result in requiring more pressure as well.