This is a weird one perhaps but over the last few weeks I've noticed that my left bum cheek aches whenever I sit down for longer than 10 minutes. It's especially annoying when driving long distances as I'm constantly fidgetting to get comfy. It's as though there's something under my bum cheek getting in the way, like I'm sitting on something lumpy! I thought it was my car seat but it's now happening when I sit at my desk. Is this something to do with my pelvis changing or something? And any suggestions to what can help?