Are you using a SC (subcutaneous) route or an IM (intramuscular) route? Most do their injections IM, but a few doctors have their patients go SC. Did the nurse instruct you to pinch up the skin or stretch it out? Did they mention aspirating (pulling back to check for blood)?
If you were told to inject SC or to pinch up the skin, then yes it should be at a 45 degree angle. If you were told to inject IM, to stretch out the skin, and/or to aspirate, then it should be at a 90 degree angle. Either way, it should be going into your leg further than what you're showing.