Congratulations on giving attention to the pinky early on.  I made a pretty big mistake early by avoiding its use.  I've mostly figured it out by now though.

The most basic concept for the left hand is that the posture of the whole left arm and the violin hold and even the posture of the whole body have to be arranged so the left hand fingers can do their work quickly, efficiently, and sustainably.  For one thing, that means, unless you are crossing strings or shifting, that movements other than finger movements should be minimized.  In particular, your hand shouldn't be moving or twisting much at all during fingering.  There are other details that I won't go into much, such as keeping the fingers curled and pressing the strings with the "left" sides of the fingertips.  That means left from your point of view as you play.

Now addressing your particular problem, unless your anatomy is unusual, the most important thing is to distribute the stretching between the first finger and the fourth finger.  The hand should not be too close to the nut.  That means the first finger has to be pulled in tight and square so as to reach back to its target.  Since you can keep the hand farther from the nut that way, the fourth finger doesn't have so far to reach, and that makes it way easier.  Practice fingering four notes on one string at the same time, and adjust everything else to accommodate that.  That will make it more likely that your hand position and general posture are close to optimal.

You are smart to look for wisdom on this and to not try to figure it out all by yourself.  You'll find great pictures and detailed explanations of it in Galamian's Principles of Violin Playing and Teaching, pages 14-18.   Ten bucks for a hardcopy or free pdf at

                    http://archive.org/details/pri.....viol00gala

My guess is that it's the best book ever written on violin fundamentals.

Edited Sun Jul 20 22:48:17 CDT 2014 to repair the link.

Ferret said
I' getting an error on that link 

Yeah, hmmm, it didn't work for me either.

I'll try again: http://archive.org/details/pri.....viol00gala

I "repaired" the link in my previous post, so hopefully they both work now.  All I did was paste the link in again though, and it didn't look any different to me.  I'll write it off as an anomaly in Wordpress or flakiness of the archive server.