Its been three weeks havent heard from my ex gf..?

Did you break up? What was your last conversation about? What do you want from your ex girlfriend? Do you want to get back together? If so, you need to give her space. Try to focus on yourself and keep yourself busy. I would not contact her for at least 30 days. At that time I would reach out to her and see how she is and how she’s feeling about the relationship. She may need some more time and therefore you may have to be even more patient than you are. If you have broken up, have you thought about dating again or is it too soon? Try to focus on yourself and do some good things for you. Exercise, eat well, and try to get good sleep in order to be able to think clearly about the situation.