Hypowoman listen to soaringfalcon. I think you are essentially a passive person and you absorb the troubles of others while seeing yourself as essentially powerless to change things. Your self-worth is so low that when some people judged you for having a child you've let that take over your life and made you too scared to even leave the house. You know logically that there is nothing wrong with having a baby at 20 - many, many people do - but you've let other people tell you that it's wrong enough to not be able to go out in public with your son. So many other things in your life have gone wrong that you are just waiting for the next thing to happen - and so you project your hypochondria onto your son. This is the problem here - this is what you are having to deal with. Not a child with disabilities or autism, your own anxiety and low self-esteem.
But here is the crunch: there are some things in life you just have to face up to, even if you're not in the best position to be able to. If you get a rat infestation, for example, you can't just think 'oh I don't really have the money for an exterminator right now, I'll have to get back to it later'. No, it's serious and it has to be dealt with straight away, regardless of your situation. It's not one of those things you can just 'leave' until a more convenient time.
This is one of those times where you're just going to have to bite the bullet - accept that you might not get a lot of support from home, accept that you might feel a little embarrassed when talking to the psych about your issues, accept that you are going to have to take control of your own life for once and deal with this social phobia for your son.
Visit the social phobia part of this forum. Read some of the threads, find out how other people cope. You DON'T have to live with this, and your son shouldn't have to, either. It's not fair on him, so stop making excuses and get this under control.