Screams

This has been Avery's reaction to going pretty much anywhere outside of the house.  It started about a week, maybe two, ago.  She screams in the car, in the cart at the store, in her stroller, in the highchair at home and restaurants.  It has become impossible to go out in public with her and I almost never return home without a headache.  I'm usually pretty patient when Avery is upset, but this has gotten out of control.  We can't figure out what has changed so drastically that she is so unhappy to be out.  Avery was even so upset at swim class on Saturday that we had to leave 10 minutes early from a 30 minutes class!  She used to love the pool and seeing all of her classmates.  She's pretty happy when we're at home.  She plays with her toys and runs around, she even likes to get on our laps and sit for a short period of time.  We're getting concerned.  We need to be able to go out in public and we shouldn't stop doing the things that we like to and that we normally do because of Avery, but a screaming spell in public is very unpleasant-not to mention being trapped in the car with one.  The only thing we can think is that she doesn't like being restrained because she wants to be up running around.  When she has the run of a place, she's fine.  The problem is, you can't just let her loose in the stores or restaurants or parking lots, etc...she doesn't stay near us or listen to come back-just like dogs, I swear.  We tried the little wrist strap thing that attaches to us and her to let her roam, but, of course, she hates it because she's limited to where she can go.  Anyone have any suggestions??  I feel like we are never going to be able to leave our house as a family and I definitely can't take her anywhere by myself.  If anyone has had a similar situation or known someone else who has please share your wisdom!!!