You dont have to have weight or size goalsif you dont want to and you can still be successful.
If you are doing a specific type of exercise you may want to improve the amount of weights lifted or reps completed or improve your km/hour on the bike . With all this weight loss will come along and fitness as well.

Swimming would be great for your back and you can have a goal of increasing lap time or amount of laps completed

YOu may even just want to have the goal of exercising 4 times a week for 30minutes as a start.

HTH