What Causes Small Popped Blister On My Inner Thigh?

Two weeks ago I noticed a small popped blister on my inner thigh. It had no top, it was just red with dead skin around it. A couple of days later, I noticed a couple more of them ( all on my inner upper thighs) they were all pretty small except for one, it was quite large. They were very sore and mad it hard to walk let alone wear clothes!!! I went to the drug store thinking maybe it was chafing and the have me some cream and gauze to wrap my thighs with. Well, most of them healed instantly and two weeks later, the bigger one is finally healing. Last night before bed I noticed a new one that is more or less in the bottom of my bum cheek :( when I got up this morning, i noticed that the other side of my bum cheek was sore so I looked and I have another one. They are sore and the spots they are in doesn t help. Could this have anything to do with sitting down so much? I was also excercising quite a bit b4 I got these blisters but haven t been able to since. I keep putting the cream on them and also put baby powder on top of that. I don t know what to do and I m getting really worried as to what this may be :( Please, if anyone can help , I would appreciate it. Thank you for your time