Postgres slow after a couple of days

Hi,

A few days ago i've installed PostgreSQL 7.4.1
After the installation, Postgres was very fast.
But now, a few days later, it getting slower and slower.

I've looked in the data-dir and i was confused when i see the big
size from that directory.

A dump (created with pg_dump) is about 1MB.

pauli# cd /usr/local/pgsql/data
epauli# du -h
4.4M    ./base/1
4.4M    ./base/17141
  19M    ./base/17142
4.4M    ./base/17143
4.4M    ./base/17149
4.4M    ./base/17158
4.5M    ./base/29156
4.4M    ./base/29175
4.5M    ./base/29184
  55M    ./base
160K    ./global
  32M    ./pg_xlog
  98K    ./pg_clog
  87M    .


Does anybody know why this directory is 87MB while the database is
1MB?


--
Edwin Pauli