Negative experience with girls caused social anxiety

Hi, folks!
First of all, I´d like to thank all of you who are engaged with helping others to cope and overwhelm one of the worst things in life - social anxiety. You´re doing a great and noble job!
I´m here because I´d like to share my experience and probably search for a solution, considering that I´m 19 years old and I virtually need to take advantage of my life.
So, the thing is that my first girlfriend - an ex-schoolmate - and I had a relationship for about half an year, but we didn´t get to have sex. We had one opportunity at a party and, indeed, we tried it, but my performance anxiety wrecked the attempts to make it all the way. Some weeks later, we stayed in my house for watching a film, so we attempted it once again, but the same problem related to my erection occurred. All in all, we had to separate because I went to study abroad, and, obviously, we couldn´t maintain the relationship despite the distance.
Afterwards, now in college, I gained some confidence in myself and, duly, got into a relationship that didn´t last for long, because of her cheating on me, so neither with her did I had a proper sexual relationship.
Then, I casually met this fantastic and splendid girl and fall in love with her. Everything was going perfectly fine until the moment she invited me in her apartment. I was prepared for having sex (had condoms), but, unfortunately, the same issue happened again. I was literally demolished, because all of my friends had had sexual experience by that time, but it never got to happen properly. That very same situation repeated itself once again and immediately after that I decided to stop going out with this girl, out of fear. I was afraid of her considering me impotent or something like that.
I reckon and admit that I have had some unreal expectations with regards to sexual performance and that is chiefly due to porn-watching, which I´m intensely trying to give up. I know the reason was performance anxiety and not some kind of an erectile dysfunction because of that porn thing.
But I really regret breaking up with this girl. I don´t have any feelings, but I feel terribly, because all the people surrounding me have an active sexual and social life, whereas I´m experiencing an authentic horror from talking to girls, because I´m aware of the problems I had in the past and I don´t want them to happen to me again. And, in addition, I care too much for the opinion of others, so if my colleagues, mates and acquaintances were aware of the failure I have experienced with girls, I´d be very, very embarrassed.
I´d be immensely grateful if someone who had been in my case could share me how to overcome that barrier which impedes me from talking to others.
Thank you in advance.