if your health is fine now then previous problems can not stop you from losing weight, diseases actually cause weight loss
. your cramps may be due to over exercising or may be due excess loss of water and electrolytes from your body. if you are generally feeling k then i will give you some suggestion for exercise, also make a proper diet chart according to your likes and dislikes and follow it.
keep note of few things about exercise
1) exercise in the morning,drink enough water before you start arround 400-500ml, also after you finish.
2)always warm up before you start , do some stretching exercise for 5 -10 min
3)when you start your actual exercise first 10 min start slowly , then last ten min also you exercise slowly then stop. do not start or stop suddenly.
4) in case you are doing heavy weight keep in mind one thing , if your body is paining or your muscle is sore next day you over did it, it can do more harm than do benefit,so you have to reduce weight and intensity
5)do not eat a meal for half an hour after you exercise, and also do not exercise for 1- 1.5 hrs after exercise