your not a lot, A LOT of guys are like you, I was nervous at first but being a body piercer for 7yrs previos to getting on, helped my desensiation to pokes..
best advice to you from experience is repitition, easiest spot to poke is shoulder and glute, poke those at first with a small 1" 25g for first week, then gradually increase some factors, go to 1.5" 23g all week 2, by week 3 you shoudl be able to stick the old 25's in triceps.. just remeber the shoulder is almost 100% painless, use a small pin, a small ammount, and a smooth injectable like test sus/cyp/enath, deca/eq..
just get used to it is my advice and dont push in the pin until your hand isnt shaking, having someone else do 1st poke also helps