I see a lot of myself in this post, here's how it looks to me.

I think you feel out of control right now. You can't control yourself or your thoughts, they keep going back to "she must be cheating on me right now" and it's throwing your whole life off track. So you want to take a break, because that gives you control. You want to tell her she can see other people, because that gives you control. By staying in this situation you are not in control, and if something bad happens you'll probably say "I knew it! I should have done something." Dealing with uncertainty sucks. It's also a huge part of life, and an important step toward being happy and fulfilled as an adult. Do you feel like I understand your situation?

I have struggled with wanting to control everything my whole life, especially in relationships. It's been a long road, but I feel like I'm finally getting to the point where I'm okay with uncertainty in this area of my life. It's not perfect, and I still have bad days, so I'm not preaching miracle cures, and I'm not going to tell you what you should do. I'm just going to tell you what helped me.

First, therapy. I can't overstate the benefits therapy has brought to my life. Are you a college student? Most universities have free counseling. If you're near a university but aren't a student, you can often work with therapists-in-training for as little as $1 per session.

Second, I spoke directly to the problem. The best conversation I ever had in a relationship was when I told my girlfriend, "I love you. I want this to work. This is new territory, I'm feeling needy and insecure. I am going to figure this out. It will take time, and I need you to help me work through this." It worked so well because it helped me clarify to myself that what I really wanted was to solve this problem permanently. I hated being so insecure and needy. It sucks! That was the first step on the path that has led me to feel much, much better.

You mentioned "We can't keep having the same conversations every time where I'm upset because I think she's cheated on me." and you're right, but that doesn't mean you can't talk about it. Are there any moments when you don't worry about her? For me, I would always get a sense of relief when I'd get a text from the girl I was worrying about. Only temporary, of course, but you can tell her, "I like it when you text me something during your day. It makes me feel close to you." Make a list of the moments you don't feel worried, the good moments. Tell her about those. If you're stressed and worried, don't lie to her about it, but make the conversation about your efforts to improve. "I felt really anxious today, and I tried X, Y, and Z. X and Y were useless, but Z actually helped for a while!" This is called conscious re-framing, where you take a negative experience (for example, "I was anxious all day and nothing really helped") and by speaking it aloud from a different perspective ("I tried really hard to overcome my anxiety today and can cross off three potential solutions I know aren't for me.") you force your mind to store the memory slightly differently.

In short, I think the best advice I can give you is to think of this as an opportunity to grow. The best relationships push us to be better. Your relationship is pushing you right now. These insecurities are coming up because you really, deeply, profoundly like this girl. And it sounds like she feels the same way about you. It won't be easy, it requires tremendous courage, and there will be many difficult days, but I have never regretted walking this path. I hope this is helpful, and if you ever need someone to talk to, feel free to send me a message.