Hey Rain,
Firstly, allow me to share my experiences when it comes to relationships.
I haven't got any. None. Zero. Zilch. I've never been on a date, nor have I ever kissed. Very few girls have been interested in me, and those that have tell me years later when any chance of a relationship are long gone. The only women I know and are in regular contact with are those from this very site, and as far as I'm aware non of them are interested in me either. How do you think I feel?
Examine the positives of what you have/had. You've been in relationships. Granted, they haven't worked out, but at 'least you have some experience under your belt and a better awareness for next time. You're also aware from this chat with your male friend that you come across as too reserved and find it difficult to express your feelings when it comes to men you like...that's perfectly normal.
No one on this earth is destined to live and die alone. Unfortunately this may be the case for some people, but for the vast majority they end up in happy, fulfilling relationships with a man/woman who love them deeply. It can take years for this to happen, you just have to be patient. Find a guy you click with, then show interest. You may find it difficult, but what do you have to lose from trying? Absolutely nothing.
Don't blame yourself for your not-so-good love life. Instead, look back on your past relationships, see what went wrong and why, then use that knowledge to build a better, strong relationship in the future!
You seem like a lovely person; I'm sure one day things will work out for you.