Workout and weight loss

Hey there. Over the last few days I've been logging all my exercises throughout the day. mainly its just situps or the number of times I've taken the stairs. Yesterday I went for a 1.5km swim, did 300 situps and took the stairs (which is 80 in my block) 4 times. Today I've done 100 situps, the stairs 4 times and went to the gym, where I did 9km on the recumbent bike, around 25 minutes on a cross trainer and 2km on the rowing machine. Do you guys out there think this is enough/not enough/too much exercise to be sustained over the next few months. I'm 15stone and looking to lose three of those. I eat so much better now and have found a healthy appetite to eat but cut down my portions and the number of times I eat a day. Sometimes I wake up and my stomach muscles hurt from the night befores sit ups but I just keep going. I'm quite muscly already as riding horses keeps me toned. Does anyone perhaps have suggestions on what other exercises I can do? :d