Serkeen you say you are not depressed. I agree with those who say that - in my opinion at least - what you describe IS depression.
'Putting others before yourself'. Why? What on earth is that all about? Is there someone in the world who is going to reciprocate your unselfishness/saintliness? Who is going to put you before himself/herself? Is there anyone?
You tried splitting from your husband, found it too lonely, got back together but you are just as lonely. Well...
So you don't find companionship in your marriage. To me, that is no marriage and you'd be better off out of it.
If DH and I did not find enjoyment, pleasure, fulfilment within our marriage then we'd split. No messing. LIfe is too short. We enjoy each other's company, enjoy everything that we do together. I don't worry my head about 'putting others before myself'. Apart from DH, there is no one in the world who is going to put me before himself/herself. All the people who did so in the past are long gone.
It may be that we expect too much of marriage, but at least, it should not result in loneliness. There was a recent episode of 'Doctors' on BBC1 where a man didn't speak to his wife for years because of some insult or injury in the past - he communicated by post-it notes. Amazing.