...until now I only accumulated satoshi...
Have you been collecting a lot of small payments from faucets? If so, it is likely that the
data size of the transaction is very large (even if the value of the transaction is low) and Electrum is trying to use a large fee to pay for it, based on the current "average" fees...
DannyHamilton wrote a really good summary of exactly how this all works here:
https://bitcointalk.org/index.php?topic=1882413.msg18710514#msg18710514If this is the case, you may need to go in to preferences and use the "edit fee manually" option, so you can specify a flat fee (hopefully you can make it more than 10 satoshi/byte, then you can use the ViaBTC TX Accelerator to get it confirmed, because if the fee is too low, you transaction make take days to confirm.)
However, without knowing how many transactions you've received, or the size of them... and how much you're trying to send... it is difficult to tell exactly what is wrong.