please send some advice im lost on how people get over there first love

how do you get over your ex bro I thought we were gonna deadass last forever and I know we're young but she was my first true love and i cant sop thinking about her bro she had blonde hair and blue eyes☹️ like that's the perfect combo and I was stupid enough to talk to another girl like 2 weeks after we broke up because I was bored and I just wanted someone to talk to and I poured out all my feelings to my ex and she said she felt the same but me talking to girl hurt her but then I also found she was talking to a boy during the same time I was talking to the girl so now I jsut feel like a pos and she said she wants me to move on because I deserve someone better so now I regret that decision so bad and she even said we could be tg rn if I didn't talk that girl