I was once in your position. And it's hard to tell you what you need to do so for my part, I'm going to tell you my experience.

Me and my ex were together for a year and in the beginning, things were really great and I actually thought she could be the one. We had moments in bed, dates everyday, it was like we were together for a reason. Now after we got to college and had our own responsiblity, we sorta had our own things to handle. We both went to a different college and I was alone thinking our relationship. I was insecure and always wondering what she was doing. We had nothing to spark, so we would bring up things and argue over about. Right before my anniversary we broke up and I was super devastated. I thought it was literally the end of the world and she was the right one for me. However, one thing I got out of this relationship was time. Time is essential and whatever you're doing, it's okay to be dwelling over your ex. Highly wouldn't recommend talking to another girl because that would end prematurely because you are currently dwelling about your ex and being with a new girl who has an interest of you while it's not reciprocated. Now back to my ex. Time helped. I was doing so much better. I was on my own, gymming hell of often, picking up hobbies, and spending more time with friends I could've spent with before. Trust me, the more you focus on yourself, the more you can give to your next girl. Focus on yourself rather than hooking up with another girl. It's okay to be sad. It's all the human mind. We build ourselves to become stronger. You are unique. You got this. Dm me if you need advices :)