Most Helpful Guy
Because you're hurt, that's why.
You can't expect emotions to just disappear straight after the break, let alone 3 weeks down the line.
A rule of thumb is it takes half the time you were together to get over them. In all honesty that's hogwash. It took me 4-5 months to get over a girl I loved for 5 years, 3-4 months to get over a girl I had been with for 3 years and then 4-5 months for a girl I was with for only a month!
It depends on many factors including the length of the relationship... but more specifically, how hooked up you were on them.
Most Helpful Girl
First of all, I'm sorry about this. I'm going through a shitty break up as well. Spending time with someone and suddenly realizing there's no more, makes it really sad. Time shall heal your wound, but whatever happens, do not contact him, it ended for a reason, and trying to do so might make it even worse. I hope you get better soon, sweetie. <3