Congrats on 3 weeks
I'm a very private person and even though married with a family I need time alone pretty often. It's not being selfish, it's self preservation, for my mental health and wellbeing.
Putting your needs first and being alone, not meeting up with people or doing stuff with them isn't selfish. It's putting yourself, your needs, your sobriety first. It's self preservation. Learning how to say no to people and meaning it is so important in sobriety.