The way you write makes it sound like she was your first love. And first loves really really hurt when they end. It sucks. It took me years to get over my first love. It takes time. Let yourself grieve and heal.

Also going forward into the future, it will be a rare ex that would be ok with just hooking up. If you just want sex, find a friend with benefits or something. Hooking up with an ex can bring back feelings for both people, for one person (who then gets hurt all over again), or it’s just not the same because both of you have moved on and it’s kinda pointless.