Questioning if I should be here at all

I've been really enjoying my job. Despite some self-doubt, wondering if I'm getting through to my students, I've loved the past couple of month and I've felt like I really found my niche, like I'd found my way onto the path where I am supposed to be. It's corny and cheesy but I can't think of another way to explain it.

Here's the situation, and any advice you can give me would be welcomed:

When I accepted the position, it was with the understanding that I'd get 20 hours per week. I bargained with HR chick to pay me five dollars more per hour than she offered because I needed it to be worthwhile for me to put my kids in daycare. I had to make enough to cover the cost of daycare.

On Thursday, I got an email saying that I could onlyclaim 12 hours per week on my time sheet and there was no budging. I was hired as an adjunct instructor and the school will only pay adjuncts for the time they spend in front of a class. I have 12 hours of class per week right now.

I argued my point with PD, about the time I spend coming up with class materials and grading work. They will only going to pay me for the time in front of students. It's incredibly unfair and I'm apparently the first person to challenge this policy.

I am so upset.

My son is finally getting settled into daycare. He loves it. I see so many changes in him, so much maturation in such a short period of time. What will it do to him to pull him out? I can't afford to keep my kids in daycare only working 12 hours per week.

I need to be working; financially and emotionally.

The tears are flowing. I am flipping out.