Not diagnosed, but I heavily suspect I have both Avoidant and Schizoid PDs. I'm only ever comfortable in solitude. Engaging in conversation is like pulling teeth. Everyone around me speaks in a language I never learned. I always walk away from every interaction feeling as though I've embarrassed myself and messed up horribly wrong somehow, and will replay perceived awkward moments over and over in my head feeling a deep soul-sucking shame I just can't escape. Simple tasks like going to the grocery store are agonizing because it'll ruin my whole day if I think I smiled at the cashier weird or stood in somebody's way in an aisle on accident. When I mess up on little things like that, instead of thinking 'oops' and moving on, my brain supplies me with an endless tirade of, "You're such a useless stupid piece of shit. You'll never get this right. All you do is mess up and look stupid and make others uncomfortable. Just kill yourself already," et cetera et cetera. It's so ridiculously exhausting. Engaging with others is so deeply upsetting that avoidance and isolation is the only way not to lose my mind. Hence, AVPD.
On the SzPD side, I don't think I'm able to experience connection the same way others are. I just don't feel anything rewarding or positive after interacting, even with people I'm otherwise fond of. It's a massive chore that exhausts me. When I was still trying to maintain friendships, I was never able to reciprocate the same level of affection toward the other party, which just left me feeling guilty. I've since discovered the only kind of relation I'm capable of maintaining in any capacity are shallow ones involving zero expectations or commitments (e.g. being mutuals on a social media platform, where we reblog and comment on each others' posts on occasion, but there's no private messaging involved). Every time someone tries to talk to me feels like a violation of my personal space. Keeping friends is a losing battle because the expectation of replying to a message, let alone multiple a day, is a massive irritation. The thing is that I am capable of holding fond feelings toward people. I'm not a soulless monster. It does make me happy to know the people I care about are elsewhere, doing their own thing. I just don't like engaging with them personally. But nobody really understands that me not wanting to talk to someone, and not having the capacity to "miss" them doesn't mean I dislike them.
In summary, my ability and desire to interact with others is nil. Makes it extremely difficult to function in day to day life.