ok thanks guys for your replies, next time I will check the number of unconfirmed tr. before giving an order for buying, I was not aware of this problem.
The exchange I am using (coins.co.th) does not allow me to chose a transaction fee when buying btc, but in the past the order where confirmed in 10-20 min, everything was very smooth and quick.
As a noob, am wondering how can the btc future be influenced by this and what are the solutions to it?
I mean, the network is very slow even now that a very small % of the population is using btc.
How can this be solved?
I think this is very important issue for our beloved currency!

Thanks