Hi and welcome to TFL! I definitely agree with checking out http://www.corneredcat.com
It's been one of my favorite go-to sites and books since I started shooting. My fiancé owns a firearms training school and he nows recommends it to his female students as well.
It sounds to me like you overdid it using muscles you don't typically use, as well as doing a lot of shooting for your first time out (and with some pretty big guns).
I suggest finding some professional training, as well as a weapon that is comfortable for you that fits you. You will know it when you hold it. I carry and shoot a 9mm comfortably. But there was a learning curve to find which gun fit me best. (I'm also the proud new owner of an AR15 but I haven't told anyone on here yet.. so shhh! lol)