I'm really confused about my life, I don't know what to do?

I think you just need to relax. Remember this quote that I heard somewhere "suffering is mostly mental". So, if you are thinking over and over again about this, you are stressing yourself out. What you think about can cause this. So, take some deep breaths and think of something else when you get like this. All you need to do is take action. In the form of making a decision. If he has cheated on you, you probably wonder if he will do that again. And, you of course seem tempted by another person too. And, you want to be in a secure, loving relationship but with the ups and downs you feel unsure. I was like this too when I was younger. You haven't secured your relationship, so you wonder how it will all go. You are also concerned about your future. But, there is no reason for uncertainty to bring you down. This is life. No one can predict the future. The only thing you can do is try to make the best decision you can with the information given. Try to decide what you want in your future. If you want marriage, do you want it with your current guy. Or is it just easier to stay with him out of convenience? Do you really want your ex back? Or were there reasons why you split. Remember your emotions and/or what lead you guys to the decision to break up. Then, don't be scared to carry out your decisions. When you're older and in a secured relationship with a guy you 100% trust, you won't feel like this anymore. It took me years of marriage before I felt this way. Now I feel like my guy will always be here for me. And, I'm not nervous about what will happen with us. He is in it for the long haul.