I think it's important for anyone who enjoys solitude to make time for it. I know having a significant other can make that difficult, but it is something you have to make time for.

My question is, have you told him you need some space? If not, tell him. I mean also tell him it's not that you dislike being around him or anything like that, but that you just need some time to unwind by yourself once and a while.

That's my two cents anyways.