20g is a pretty big needle even by my standards. I use 22g and thats considered large. Look on ar-r.com and get some sterile cottonseed oil and cut the prop 2:1. Spend extra time massaging the injection site. Make sure you inject slowly. 1.0cc takes me about 15 or 20 seconds to depress the plunger. Try going for a walk after words to work the oil out of the muscles. Vary your injection sites depending on the muscle you're using. Sleep with a heating pad on the injection site. Take 800mg of ibuprofen for inflamation. These are just a few things that help me and others here with injection pain