Putting myself in your boyfriend's shoes:
The time alone is easier, and has already been dealt with. I live in my head a lot, and coming out of there to interact with others is exhausting. It's not a problem where I don't have anyone I enjoy interacting with, but when there is someone - as you are to your boyfriend - I can end up tiring myself out and being bad company. I've now learnt to steady myself better and, though I'm sometimes plain unavailable, when I am I can get on with enjoying their company. It seems your boyfriend is good with knowing when he needs alone time, and isn't afraid to say so - which, I think, shows trust.
As to the text - first, I wouldn't know what to say. There's polite acknowledgement - 'thank you' - but that may not be appropriate. There's also polite reciprocation, but that can seem a bit odd because I wouldn't be with someone I didn't consider myself lucky to have in my life, so it would be stating the obvious. I think such affectionate communication from Aspergians often comes in deliberate, practical actions, such as his bringing you medicines and staying with you, rather than words. Over time, I've learnt the importance of words, but it still takes a particular awareness, as my default is 'if I weren't interested in you, I wouldn't keep spending time with you'.
There's an idea that we should judge by actions rather than words. To me, it's easy to throw out pretty words. It takes effort to find and carry out ways that show I care about someone. Going by that, he seems a solid man, and you a thoughtful woman.
Good luck to you!
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Of course, it's probably quite a bit more complicated than that.
You know sometimes, between the dames and the horses, I don't even know why I put my hat on.