Do you ever compare yourself to people you went to school with?

I was working the other day and I served a guy who I went to school with. I was so desperately embarssed when he came through my checkout. All I could think was, you are a navy lawyer now, and here I am still sanning groceries like I was 8 years ago. Sheesh. What a way to make a person feel worthless.
Of course some lovely friend of mine kindly pointed out that having a family is an achievement. Which of course it is. Let's face is, it's feckin' hard raising kids, but I am so desperate to acheive something personally for myself. Just for me. The flow on effect will naturally benefit my kids, but I need SOMETHING.
Lately I have been thinking heaps about going back to uni. As conceited as it sounds, I have too much brain power to be wasting it scanning groceries and stacking shelves. I Do however like the money it proves,even if it is a measly 17.35 an hour. I do sometimes have moments where I am thankful the job doesn't require your brain to be ticking at all times, and the job is flexible enough for now to make it work with my families needs.
Study on the other hand provides me no money (short term in the least) and huge amount of brain power and very little flexibility, but I can't help but wonder if it would be better for just me. If I put my family aside for one moment. Study would be for me.
I don't know what to do. Husband (in all his supportive ness) just told me "You do what you want to do, and then just tell me what I need to do to enable you to do it" What a fantastically generic supportive answer.
Perhaps what I actually need is an epiphany or some clarity.