How can I tell who is the right guy for me?

So I used to go out with this boy rob for about a year we broke up and I started dating another boy but I broke up with him because I still loved rob.. me an rob got back together and it was better and then we broke up again but we stayed friends and we both said if we meet and things click we wud try again.. basically our relationship would never be off the table. Where I was so upset after breaking up my friend set me up and I didn’t want a relationship at the time I wanted to be single and just be with the girls but I felt pressured and ended up dating this guy john and he asked me out and I said yes thinking it was fine.. but 4 months down the line I am missing rob.. we have met up a few times just as friends before and we haven’t spoke for 2months till his week.. and it was because I really missed him I love his family we get on soo well.. and things I miss about rob I dont see in john.. and I just cant see me and john working but I dont know whether me and rob have a chance like whether it is worth breaking another relationship or wether its just a case of wanting what you havent got? I dont know whether rob is right or wrong? But to be fair it wasnt his fault we broke up and he never got with anyone else inbetween.