Broke up with my girlfriend from a 3 year relationship. advice/help?

So, i have known her since elementary school. been best friends until we started dating in grade 11. we've been through a lot - prom dates, cutest couple in high school, ALOT. She was my first and true love. Im currently in 2nd year of university. This summer has been extremely weird to me. She needed space from me. I couldn't, so i didnt. She went to Cleveland for a trip for 3 days. and then when she came back. she wanted to break up with me. Something that i never imagined us to be. I gave her my whole life. i trusted her with everything. Then i had to ask her a million times, until she told me she had feelings for someone else. this was the hardest thing i ever had to do, so i told her that she cannot break up with me, and that i had to break up with her. This happened last night. And, the hardest part is that i cant stop calling her. i cant stop seeing her. She knows what she has done wrong, and shes hurting. She wants me back. But i cant give it to her.Broke up with my girlfriend from a 3 year relationship. advice/help?
I am sorry to say this, but I believe that sometimes people just change without us and sometimes we are the ones who change. If you think you won't ever feel the same about her then you should let her go.

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