JonRah I'd call your midwife just to check what they think, it may be some pulled muscles but if it eases your mind then don't hesitate. I called my mw with the dumbest questions when pregnant with ds, and I've already called her 3 times already LOL she must think I'm a fruit loop. Hope you are well, elevate your legs and keep resting. Oh if you were wearing something slightly with heels that may have caused slipping? I slipped all the time and had to be in flat shoes from about 10 weeks with ds because my balance was so bad.
Oh the sleeping comfy thing, it's ok to sleep on your tummy you can get pillows, just don't do it if it's too uncomfortable but your body will turn you over. Sleeping on your left side is meant to be the best way, but through my pregnancy the only way I got comfy was to sleep on my right side because of the way he lay inside my stomach. A pillow between your knees can help keep pressure off your uterus and stop you from rolling your stomach, and also a pillow wedging under your side so you are lying on it can help too, especially when the bump gets bigger.
Anyway better go have my second dinner. Hope everyone is well sorry if I missed anyone.