I had a surgical abortion 1 week ago but the next day i went back to the gym doing 1 hr cardio as an daily routine but i constantly gaining weight.

Other Cause: If the fetus has been removed, that can't be the cause of ongoing weight gain. Depending upon the gestational period of the fetus, it takes time after its removal for the extra body water to be removed as well. Your workout should continue as you consult your physician to check you for other causes of weight gain, like thyroid etc.

Wt: typically; weight gain is associated with calorie intake especially carbohydrate intake------if calorie intake is greater than calories burned = weight gain unless you have some endocrine dysfunction such as diabetes ,hypothyroidism etc---then weight gain is a more complicated entity ---which you should see your doctor about