my play counts for many songs in my library are completely wrong now

Okay, ever since itunes updated itself on my computer last week, the play counts for many of the songs on my various playlists are completely wrong. Some of them still seem to be accurate, but some songs that I've played over 100 times in the past year or so are now reading as having only been played once or twice. How can I fix this, as I like to keep track. Also, i-tunes seems to take longer to open up on my computer than it did before the update.