Clint, love. You had a short relationship a couple of years ago, she ended it, you were distraught.
You restarted the relationship recently, and already can see that she's apparently checking out again.
With the utmost respect, she is not that into you. You deserve better. The events of the past have made you needy and paranoid. Both highly unattractive.
she ended it before, for a reason, you have to understand that, and lived apparently happily for a couple of years without you. You however pined somewhat for you.
Your self esteem is low, perhaps because of this woman, perhaps it already was.
Running after her, or having meltdowns are not the way to live. I have to say that if anyone had a melt down with me as you described it, that would be enough for me to take to the hills.
You need to demand better treatment of YOU by those you wish to spend time with. The more you keep coming back for more of the same, the worse you will get treated.
This relationship is unbalanced, which only ever serves to create a highly unhealthy and deeply damaging dynamic.
If I were you I'd end it with HER. Show HER that you deserve better. If she lets you go, then you know where you are and can move on to better people. If it jolts her into thinking that she can't get away with treating you like that and she starts respecting you, then it might be a basis to work from.
YOU have do demand and expect better for yourself. YOU have to realise you deserve it. Otherwise this pattern will keep repeating itself and your self esteem will be in tatters.