You know that a guy or a girl isn't right for you when you are clearly his or her second choice or option.
There's always something more important than you. His ex-gf, his friends, his alcohol, his everything else and when it's convenient, then there comes you. Otherwise, it's a no.
After knowing that someone got back together with the ex-gf, or in any case ex-bf, it's time for you to get out from that sight. Instead, if you choose to stay on, forcing the particular subject to choose between the ex or you, then for obvious reason, the person will choose the ex, and not you because you appear to be so pushy, so brash, you have just helped him to choose who, then you get all depressed. For the start, you should not even had stayed on. But, for whatever stupid reason that may be, whether it's out of loneliness or desperation, you will always be his second option because of what you are.
It's distinct enough that you are insignificant to him. Going all over him will not make you more compelling to him. Instead, the gap and distance will just grow larger. Perhaps, it's your well-being. If you are desperate inside, people can sense it, regardless how bad the senses are.
If you have appeared to be 2 guys second options, something is wrong. Maybe, you are a second option material and nothing will going to change that if one continue to appear as desperate as this. It's not only desperation, but if you do not have any pride in yourself, which means, there's no respect for yourself, give me a good reason why others should respect you.
When you find out that you are the second option, the best is to leave for good and never ever turn back.