Hi Jotosuds,
I can agree with what you're saying. I've written dozens of songs, and they quite often use the same progressions! Another thing I find is that I often come up with a melody when I've no access to a guitar (my main instrument). I try to memorise it, or sometimes record it on a micro-cassette for later. When I finally pick up the guitar to work out some chords to match the melody, lo and behold it's the same sequence!!! (Often the G Em C D one, which I THINK in Roman numeral form is I, VIm, IV, V, which is the (again I THINK!), known as the doo-wop loop).
Ideas to get around it?
1) Write with the guitar, and start with an unusual (to me) chord. So instead of strumming a G to get started I'll strum a B. That way, I won't just automatically go to Em, or at least , if I DO, then it won't sound the same!) Or I'll start with an "uncommon" minor chord like Cm).
2) If you usually write with a guitar, write with a piano.
3) As someone hinted at before, take a selection of songs that are a style (or quality?) that you would like to achieve, and either transcribe them, or cheat and get the tab from the net. See what chord progressions they use.
NB I read a superb article about the Beatles in the UK mag Total Guitar, which basically looked at about 25 chord sequences that they used in their songs, and explained the theory behind them. It also gave example where the sequence had been used in songs which the Beatles had almost certainly heard, and probably PLAYED, during their Hamburg days. The point is, they had to learn how to play hundreds of popular songs, and by doing that, they also collected library of chord progressions which they often incorporated into their own work. Like 'em or not, they knew how to write a hit song...!
Hope some of this helps.
Cheers,
Mscmln.