Ask yourself why being alone fills you with so much emptiness.

I used to be that guy who sleeps around, then a serial monogamist in one period of my life, then that guy who sleeps around. Now I'm that guy who lives alone. I've been alone for 5 yrs. That's a long time. Most people die of lonsomeness. They don't understand how a person can be like this and be happy. And I've come to be happy by myself. At any time, if I found someone, I'd go for it. But I haven't. Other people like my family 'worry' about me. I look at their relationships and they are all crap. Absolute crap. I see how they interact, how their relationship could be defined as physical colocation with an ongoing attrition of daily mild abuse resulting in disillusionments, deep sadness of unfulfillment and disappointments; and a sadness from feeling 'trapped' or 'resigned to this post', stuck in the status quo, eternally because they'll be damned if they are going to change theirselves in any way.

Then it hit me--everyone is sad, me, them, you. Everyone is sad because at the end of the day you come into this life with someone else (your mom) and then you die alone, and all this time in life has been an opportunity for you to figure out how to forgive / accept and love: yourself. And doing that requires being complete with the tools you already have, and making peace with your own mind before you take the biggest journey of your life which is counterintuitivley death.

So my advice is to go deep into your reasons for feeling lonely and there you will find the answer to why things aren't working out with others. Because the other is really just an expression of a part of yourself, buried under illusions.