I joined a biggest loser challenge. Need help!

CeeRawr89

First official weigh in is this Tuesday.
I currently weigh 144:

I took these pictures four days ago. I've never felt comfortable with my stomach, but I need something to keep me going.
All the extra fat I currently have sits in my stomach area. Hello ruined core due to a baby!

Now, I don't think I really need to lose much weight, but my goal weight is currently 125, as I am 5'4" give or take and that is what sits best on my body type and shape. Before the child I was a very natural thin person, I used to be 110 at my "heaviest" then I gained a bit of weight, and then found out I was pregnant.

It's been a struggle ever since.
I've noticed that my arms really need work, and I want to not necessarily lose weight, but if I do on the way, that's good too. I'd love to add definition to my arms and my stomach area.
I need to know what to do, so I can make this challenge worth my while.
My ultimate goal is to be in a bikini by summer time, and wear it with confidence.

I don't want to lose my legs, cause they are great looking legs. Ha ha.

I want something that can also help me..have a nice-r booty.

Tips and inspiration and motivation, greatly appreciated!!!!!

Posting here, because I figured I would get better feed back!