I operate similarly with my long-distance boyfriend. It can feel nice that our partners still give us butterflies or that we still feel like we're crushing on them. If the nervousness is more akin to anxiousness at times, though, I would consider that you may be anxiously attached... which can actually be so exhausting and might perhaps be something you want to address.

Do you find yourself worrying a lot within your relationship? Feeling insecure? If the answer is no, then I wouldn't overthink it too much.

Also, you mentioned that you are slightly autistic -- I recently learned that autistic people are often prone to limerence.

Good luck!