Well, for starters...by the sound of your post im guessing you are prob a freshman in college. A 2.5 is very easy to boost up with around 90+ credit hours ahead of you. It is VERY feasible. Obviously, you wont get it up to a 4.0, but you dont need a 4.0! How come you are eager to go with the biomedical engineer major? It sounds like you are extremely disciplined with you weight loss. That is a good sign. It means you have the ability to dedicate yourself in becoming successful at something. Your biggest task now is to figure out a balance between working out and school, the latter being the main focus. I would probably be considered a "workout-aholic" but i always make time for my school. I workout 5-8 times a week. However, school is the most important part in my schedule. If I am going to have a busy day, i plan ahead and either wakeup early to workout, or simply take a day off. However, if you take a day off, just dont go to burger king and eat 3 whoppers! I am sure you maintain a strict diet and you should always abide by it regardless what your busy schedule is like.
I, personally, stick to a 2000 calorie/day diet. If i dont workout one day, I eat 1600-1800 calories to make up for the calories i didnt burn. If i workout 2 times a particular day, I may eat 2400-2600 calories that day depending on how rigorous my workouts are.
The point of all this is that you have to find a happy compromise. Afterall, there are only 24 hrs in a day! Play with your schedule a bit and find a routine you can stick with!!! But remember, keep school first.
Hope this ramble was of some help!