What Causes Painful Red Rashes With Swelling In Arm Bends And Shoulder Blades?

My name is adam, I am 27 years old. The weather has been changing here where I live. I have been working out in my garden and I noticed the other day after working that I started to get what looked like a red rash on the inside of my right arm, where the arm bends. It has been getting progressively worse and worse. The area is now swollen and painful, I can hardly bend my forearm towards my chest without it feeling really uncomfortable. On my other arm there are patches of the same looking pumps but they are not concentrated to one area. The rashes on my left arm are towards the back of my arm about 6 inches above my elbow and some near my armpit area.. the rash is also on my upper shoulder blade. The area behind my left arm above the elbow has obviously been weeping a bit because I can feel hard sap like texture on the area.. but it isn't as painful as my right arm. It itches like mad.. it doesn't look like poison oak, sumac, or ivy, it looks a lot different. more scaly.