Did you thought you can shred after you've played some exercises for a couple of months ? It's normal the progress goes slow. Play little licks like these and repeat them endlessly untill you can do them quiet fast. Try to use a metronome and play them all over the fretboard. They have(well, they still do) helped for me. The first thing you need to learn when you want to shred is to make sure you're fingers are fast enough and can handle any position.
(try to copy the licks in notepad or something with a descent font so they don't are crammed together)

The fingerings are written above it.

[1][3][4][3] [1][2][4][2] [1][2][4][2]
-7-9-10-9- -7-8-10-8- -7-9-11-9-

[1][3][4][1][4][3][1]
--------7-------
-7-9-10---10-9-7 etc. etc.

Try to find your own combinations and try to find combinations who YOU find difficult. Practise slow and slightly increase speed. Don't forget to alternate pick. When you can do 'em properly bind them together in long licks and then start to practice on them. Do the same with every type of exercise you want to to, sweeps, taps, fingerpicking, whatever. It helped me ALOT to break verything in several pieces. It doesn't only improves the thing you are pracrtising but it also helps you with other styles.

Be patient. It's a matter of years of long practise. I'm just telling you what I've learned and still am learning. I am far from a shredder, but I wouldn't wanna be one either. It isn't all about speed!

Latz, Gulder.