it sounds like you'd like to have a six pack, which is a muscle group that *everyone* has. some of us don't see them simply b/c our body fat covers them up. assuming that you are a male, you need to have less than 13% of body fat for your six pack to start showing. once your body fat is around 10%, your packs should be washboard-like.
one important thing to understand is that you simply
can't target train your abs. no matter how many situps you do, your abs won't show until you reach the mentioned percent body fat. that's why you see skinny folks who hardly exercise would have solid abs. it doesn't necessarily mean that they are fit/healthy, though.
i'd say you should focus on cardio. your cardio sessions are way too short. in fact, they are shorter than someone (me) who's trying to gain weight. 5 mins of cardio is a warm up, 10 mins is the minimum for health benefits. you should be doing at least 20-30 min every other day if you wanna lose weight.
also, the intensities of the exercises you are doing are modest at best. a general rule of thumb is if you can say more than 5 words without catching a breath, you are not working out. instead of biking, try to
train yourself to run 5k every other day. then, train yourself to run faster (5k under 28 mins). while ellipticals are designed to prevent potential injuries associated with running, i've always felt that running (or even treadmill) is more intense. also, elliptical won't help you to chase a thief in real world. an important note on cardio equipments -
do not hold onto the machines. by doing so, you are shifting your body weight to the machine and your workout will require less effort. your body will also lose the instinct to balance itself in the long run. lower the intensity if you are gonna fall.
at age 14, i would not suggest any diet unless it's recommended by a health professional. your metabolism is going strong and you need the nutrients to grow (and you don't sound like a big kid to me, really). have a trainer/coach show you the
correct forms before hitting the gym. you won't believe how many idiots out there w/ awesome bodies but ended up hurting themselves cos of bad forms.