HI, thanks for using healthcare magic It is possible that your pregnancy may be uneventful despite the sinus tachycardia but you would need to be reviewed by your doctor and cardiologist to make sure. The atenolol would likely need to be substituted by another drug if you conceive because it cannot be used in pregnancy. In terms of the weight loss, this can be achieved by change in diet and activity levels. There are different diet plans available. The most common would be the low carbohydrate diet and the low fat/low calorie diet. You can choose the one that best suits you. At least 150 minutes a week of physical exercise is recommended. I hope this helps