Sensitive skin on back of thigh

[Hbsoderberg]

Hello,
Today my skin on the back of my thighs became really sensitive. This has happened a couple of times before, usually once or twice a year for the past two years. It lasts for a day or two when it occurs.
It always happens on the back of my thighs. The whole back portion of my thighs are sore and sensitive. There is no visible rash, either. If anything rubs against it it hurts. It's weird though, because if I put pressure on the spot it doesn't hurt, but if I touch it lightly is is sore and kind of feels like a sunburn (I haven't been in the sun at all recently).
I recently had my blood tested for my physical and everything is fine and my doctor says I am healthy.
If anyone can help me out it would be greatly appreciated.

[Hbsoderberg]

***forgot to add in that I have missed the last five days of my birth control, maybe that has something to do with it happening right now? But again, this sensitivity happens at least once a year so I just want to know what it could be...