Is someone deliberately making me feel guilty?

I find that in recent months, every time I speak to my grandmother, I come away feeling like I have done something wrong and I feel horribly guilty. She never specifically tells me I've done anything wrong but she has what I perceive as a disapproving, disappointed tone and a stern expression. I have to say I am actually fearful of her now and wouldn't dare ask if I've done something wrong.

I know this sounds rather pathetic, especially as I am a grown man (in my 20s) but I have high functioning autism so I'm not really like a typical adult, I'm still really like a teenager in my emotional development.

I find eye contact a great challenge and I find it very draining being around extrovert people who like to make lots of eye contact because it makes me feel obliged to look at them which makes me very uncomfortable. This applies to my grandmother and I am wondering if she is fed up with me because she mistakes my autism for disinterest or aloofness. But she has known about my autism for several years and I have explained to her I do not find eye contact easy, so I'm not so sure the reason for her dissatisfaction.

Basically, I want to know if it is my problem or if she is just being passive aggressive and manipulating me? I told my mum she drains me and makes me feel guilty but my mum said she doesn't feel drained when she sees her so this makes me think it's my problem.

I hate this constant second guessing myself and not knowing whether I should really be feeling guilty when I don't know what I'm supposed to have done.

Well, having autism puts you in a bit of a different position than most of people, but you're still human. Most of communication between people happens on a non-verbal level, which includes the tone of a person's voice you mentioned. Don't be ashamed of feeling this way even though you're in your 20s, grown people have equally fragile emotions and I wouldn't even say being over 20 makes you much of an "adult", since your brain is still developing.
I don't really know the situation you're talking about, but usually when you're even afraid to ask someone what you did wrong, it is not without a reason. I don't know your grandma either, saying she deliberately makes you feel guilty may be going a bit too far. Certainly there is something off about the way she acts and she's unwilling to discuss it with you openly, choosing to be resentful instead.

She is very changeable. Today I spoke to her and she was perfectly fine. I think perhaps she has off days due to stressful family circumstances as 2 of her children (1 being my mother) are currently not well. As I have social anxiety, I think I assume that when she is fed up and irritable, it is because of something I've done.

She may be feeling unwell herself. Perhaps you could find a way of asking her how she is feeling, without making it about you.

When I am very worried about something it shows on my face. Most people are not troubled by this but there are a few people I sometimes have to interact with who totally freak out. They assume my expression is all about them. I cannot imagine why! My interaction with them is very limited and never with only them. Why should my face be about them and not any of 10 other people?

I am sorry you feel this way! I know the feeling. When I was growing up I had a Mother who was all about guilt, and blame, and shame. Growing up I often I felt someone was trying to make me feel guilty when it was about me, my guilt, and my mother of a Mother. I still feel guilty a lot, about silly things as well as real things.

It could be that you are feeling guilty because you think you should have done something you didn't do (as opposed to feeling guilty for something you did), or you just feeling guilty because it is your normal fall-back status (me), or she could be (consciously, but more likely unconsciously) manipulating you.

I have someone in my life who is passive-aggressive, and guilt-manipulation is common, though they do not do it deliberately. It is a defense mechanism. I think you should just talk to her about it, if you feel that is an option, in your situation. It is the best option, if the personalities will allow it. Good luck, I feel for you.

I can really relate to the lack of eye contact. I have a mood disorder and I find it very difficult to keep eye contact with my peers, coworkers, and relatives. I did not do anything wrong, but it is a mood that surfaces which I am trying to cover up: mania or depression.
Then they to make me feel unprofessional or unethical. Then I get anxiety and I want to cry. It is so petty. It doesn't mean a thing. I am trying to overcome my anxiety and panic disorder. I am sober, and I let people make me feel guilty. I think I have a mild form of adult autism.
Sometimes, I just understand that other people may be having a down day also. They can take their guilt out on weaker individuals. Keep up a good attitude.

Do you only feel this way when you are in the presence of your Grandma? If so, then it's her problem.

My Dad behaved like you've described throughout my childhood. Even in adulthood, on some days I would ring him on the telephone or visit him and he'd be short and snappy with me one day - moody, impatient and short-tempered, and perfectly fine the next day. For years I would come away wondering what I'd done wrong and analysing my behaviour over the week - was it because I said this or did that?

It took me until my late 30s to realise that it had nothing to do with me. I can't remember what it was specifically that led to this revelation, but there was an event/conversation. I've realised that he finds it hard to cope with normal life. If something does not go to plan in his own life or annoys him (unrelated to me), he will just be vile to everyone around him all day. It's very damaging for a child to be raised that way, because it causes confusion and you always blame yourself.

I bet your situation has more to do with your Grandma's personality/issues than it does with you. If there are things about you that irritate her, then that's her limitation as an individual. I would be spending as little time with her as possible, and distancing myself emotionally from her when in her presence - observe but don't absorb.