I won't describe this well but here goes. I am 35+5 and every now and again it's like one or both of my legs almost give way from the very top as they join to my hip. I need to grab something for balance. It lasts only a few seconds and is painful/uncomfortable. It's like something has gone out of place and it quickly fixes itself but I am worried it won't fix itself one of these times. It's mostly on the right side but occasionally left and sometimes both. Iam very very slight in build and have a huge bump. Any ideas what this could be?