If it has been three weeks since you stopped breast feeding, then by now, the milk should have dried up as well. If your body would have followed this course, your periods would have manifested by now. However, if not, there is nothing to get unduly alarmed about. Every woman's body is different and it reacts differently to these situations as well. If you have not got your periods yet, there is certainly nothing abnormal about it. Though if it would make you feel more comfortable, you can consult a gynecologist who would, in all likelihood, confirm the same.
If you are worried about resuming sexual activity, then you should know that there is certainly no problem with that. However, you would need to be careful if you do not wish to conceive again quickly. It is always better to take precautions in this regard. And while it is mostly true that most women do not conceive after delivery till they have experienced a full and normal menstrual cycle, this is not the rule. There is no definitive information that would claim so either. So you must take appropriate precautions while having sex to ensure that you are well protected against any unwanted pregnancy.
answered by G M