I didn't know whether to post this in muscular or bone problems so I'm posting in both (sorry).
For over a year now I've had problems with my lower back. Whenever I lay down on the floor/sit on the floor leaning against a wall or something/and recently lay on my stomach playing on my laptop or whatever I get this pain. It's a shooting pain whenever I move and try to shift positions in any way.

In the last month or so I've got this shooting pain in the sternum on two or three random occasions. It's like stinging that goes away after a second or two. I didn't think the two problems were related ,but last night I was just hanging out and I got the sternum pain 3 times over the course of the evening and this time there was a slight, accompanied back pain.

I was just curious if anyone thought this sounded familiar. I didn't get my back checked out b/c it seemed silly-I would just stop laying on the floor if I had to. I'm a young 20 yr old girl who works out a few times a week, but I never really overexert myself in any way. If anyone has any helpful ideas they would be greatly appreciated. Thank you.