I feel really uncomfortable around other people

Thanks for sharing your concern!  I think you'd be surprised if you knew how many people feel the same way.  Being in crowds can provoke anxiety (one of the symptoms of anxiety is irritability or anger, like you described).  For some people, that's just because of their personality (if you tend to be more introverted, being around lot of people is really draining).  For others, it can point to a diagnosis of social anxiety.

I'd recommend starting by writing down your self-talk.  It sounds like you are telling yourself a lot of negative messages (as you mentioned, having imaginary conversations and assuming people are judging you).  Write down the thoughts that are leading to you feeling terrible and crying.  Maybe that's:  I'm stupid, Everyone else is having a good time so I should be too, There's something wrong with me.  Just writing these down is an important starting point because it allows you to be objective to your thoughts.  When you see them on paper, you can start to identify the lies and reframe them.  Next to your negative thoughts, write some positives:  I have something to offer, I'm okay the way I am, It's okay to prefer 1:1 relationships, etc.  Hopefully even as you read some of those suggestions, you feel a little lighter and more okay with yourself.  

Take care!

So amazing that you are aware of your social anxiety and distress with others you are in relationships with. You have taken the first step toward a journey of healing! 

Secondly, make an appointment with a therapist who specializes in neurofeedback and biofeedback treatment. A test is needed to determine which areas of your brain are ‘on’ and which areas of your brain are ‘off’. Then it will be focused treatment which will speed your healing.