help needed... having probelms signing into the psn network....

i have been experienceing this problem for about a week now... i don't know what to do i tried everything... i cant sign into psn at all and i can't go online to play my games... all i can do is play my games and unlock achievements but as soon as i turn my system off they are all gone cuz im not signed into save them.... i could still also go on the interenet.... which means there is no problem with my wi fi... there is something wrong with the network its self... it won't allow me to go into the playstation store as well... if anybody can help me that would be greatly appreciated... i talked to a few of my friends and found out they been having similar problems... please help me...