Hair intervention

When I was in high school, I was gross. I only showered like twice a week, but somehow I still managed to never get ousted for my bad hygiene. I'm lucky because I don't really sweat much and I'm just generally not a stinky person. And my hair....it just always looked REALLY cute. I have no idea how this is possible. It was long and lush and beautiful - even without proper grooming. I would wake up in the morning and literally not touch it and it looked perfect.

Cut to today. Something has happened in the last 12ish years that has not been good for my hair. Whether it be more regular bathing (but, let's be honest, I still only get it in like 4 times a week) or having a kid or that my eating habits went to shit...I really don't know. But basically, my hair kinda sucks. I have one particular problem which keeps it from looking good. I don't know what to call it, but basically it just goes all Medusa on me. It starts out something like this:

And then by like 11am, it looks more like this:

I have no idea how this happens. My hair is not curly, I do not live in a humid climate and I sit at a desk all day. But something happens between the time that I put it all in a ponytail and 3 hours later that makes me look like I ran a marathon. In Arizona. In July. At noon. And before I know it, I look like this:

And this:

And this:

There have got to be something that would tame this yucktastic mess on my head. But being the (formally) spoiled hair haver that I am, I never learned the fine art of hair products. So please, for the sake of my coworkers, enlighten me. What do I need to put on this rats nest??

By the way, ignore that pesky double chin that seems to have arrived with my 3rd trimester today. That thing seriously came out of nowhere.