I have excessive pain when I put pressure on any muscle.?

I am 38, I have Degenerative Joint Disease (form of arthritis), but lately, I have notice that when I "scratch" an itch it causes significant pain under the skin. It's not an abrasive pain, it's a pain that feels like someone has hit me with a baseball bat. No, I'm not scratching really hard, I get an itch & when I scratch it the pain is so intense that it nearly takes my breath. It's really hard to explain and put into words but it feels almost as if I'm going to leave a nasty bruise just from scratching an itch. I've checked and I'm not leaving any bruises, it just feels that way. I've tried doing internet research but it's SO hard to put into words, I've been unsuccessful. Is there anybody out there that has this same physical issue or anybody know what it might could be?