13 weeks pregnant

I'm not sure about your definition of heavy weightlifting but I continued my gym 5 days a week with running on treadmill and machines and dumbbells until a few weeks before my due date for both kids. It is important to keep fit even during pregnancy which will help when labour comes. However, double confirm with your gynae and be honest about what exercises you will be doing. As long as gynae gives the green light, go for it!