So it seems common that baby squeezes me/self while nursing...

...and she squeezes so hard that she cuts herself (usually the outside of her knee) when her nails are too long. But she also squeezes thin air and squeezes her blanket... its kind of excessive.
As soon as she became verbal (about 2 months old) I started signing to her and -surprise- milk is the most consistent. So when she started squeezing thin air (tentatively at first) I got excited that she was communicating milk. But she does it a lot and after we are done nursing. Is this common?

i.e. She "signs" and then we nurse. While nursing she squeezes my arm, her leg, the blanket, thin air, etc. Eventually she rolls away or unlatches and she might keep squeezing thin air under her chin or at a toy for a bit and I double check that she is done. She is so I just ignore her "signing". It stops after a while. She never "signs" and then refuses to eat, except once.
We were in the car (she hates it when I leave her lately and she's always hated the car seat) and she was hungry and didn't want to be alone so I was going to sit back there with her after I nursed her and DH would drive. When we are alone I might nurse her and when she finishes I'll go up  front and we drive away with her crying, full but lonely and bored and strapped into something (why she doesn't like the car seat, she hates being strapped into anything). So I finished nursing her and I put my boob away and DH turns the car on and I am getting on my seat belt and she starts crying and "signing" milk. So I say, "wait" to DH and pull my boob back out and she latches on and then looks up at me and unlatches and smiles up at me. I tried but she was done nursing and I put my boob back and she and I played with toys and then my hand until we were at our destination.

The point is, that it seems legit that she is signing so why does she keep doing it after we are done nursing and why does she squeeze herself during nursing hard enough to break the skin sometimes?

Also, she'll squeeze the toys she is sucking on like her milk "sign" and for a while now she has preferred to bunch up her naptime or bedtime blankets while nursing and she still does that intermittent with squeezing. Its just a lot of squeezing. AndalsoBTW, she was gripping things and picking up and passing hand to hand for about a month before she began "signing" "milk".

I have been doing other signs for her: "diaper", "sing", "play", "read", "naked", "more" and "all done". Some are maybe a little hard for her to grasp the concept of at her age (5.75 months) like more and all done. Of all of these milk is the easiest. She doesn't seem to sign any of the others except once or twice we thought she was trying diaper but couldn't swear to it as it is, I'm sure, beyond her physical ability to do properly.
So, since she seems to be signing is she just fascinated with her new ability or has she some sort of tic or quirk that should concern me? The post about autism and twirling hands is what raised any concern in my worry-wart mind, I have to confess. I know I'm pathetic with worry sometimes.

Also, completely unrelated but I found a questionable looking bit of paper napkin in DD's poop diaper the other day. I think she ate it. I've seen her "bite"off a chunk of paper towel or napkin before so... oops!