Motivation help and other tips

Hi!
I am a 18 year old girl, and I have recently gained 17lb. I am 5'5" and weigh 176lb, but I would really like to get down to 143-146lb. I am a footballplayer, so I want to become fitter, not just loose weight. My main goal is to feel better about myself, and not be so self-conscious when I'm in a bikini for instance. Also, I would love to be able to actually look and feel good in a tight dress or skirt like all my friends do - haha, some of you might be shaking your heads, but I'm a teen, it's important! :)

I am thinking of doing the insanity workout starting in december or the week before, and I think I might hire a personal trainer after Christmas. My main problem is that I lack motivation to actually get up from my bed and do it. Does anyone have any tips for how I can make myself actually get changed and go do it? Or if you have any other suggestions for me I would love that as well.

Also, I am a bit of a food lover. I don't eat too much bad stuff, but I can eat better. if anyone have any easy to follow food rules that they would like to share, I would really appreciate it. I am living in another family than my own, so I can't really expect them to change their meals for me.

Thank you!