what's my problem?/ how do you know if you've pushed yourself enough?

[BlueBison17]

This was me maybe late 2011
http://bodyspace.bodybuilding.com/im...BOoIzBoCnL.jpg

this is me
a few weeks ago
http://bodyspace.bodybuilding.com/im...GChqycbwqE.jpg

or you could just go on my profile and see the progress, anyhow the summer of 2012 I was only doing insanity, not lifting at all and didn't get to it again till the start of September, a few months back.

Is it just me or does it seem like I've only lost weight and been a bit more "defined"? Doesn't look like I've gained much muscle....
I mean I think I work hard at the gym, sweating and trying to push myself, always varying the workouts so I avoid any plateau's usually it's a different set of workouts each week.
so either my problem is that I'm not working hard enough or I'm not eating enough.
I mean my workouts from Sept 2012-beginning of Dec 2012 was a upper/lower body split routine whereas last year was a three day split.

And as a college student who doesn't currently have a job, I don't have the luxury of buying mass amounts of food, nor do I have the time to prepare meals every three hours. It's probably the latter that's the problem, but how much fat can I be expected to gain if I do a clean bulk?
lets say I was 18% bf, if I wanted to gain say 15 pounds of muscle, which takes maybe half a year to achieve? how much bf% will I be at the end of that time? And is it true fat turns into muscle? I heard that it was better to bulk if you had some fat on you vs being skinny, or is that just Bro science?