How long have you been working out for?
At 5'11" and only 155lbs you haven't yet discovered how to train to grow nor how to eat to be bigger. I appreciate that you're making the effort at five meals per day but, at 155 lbs, you're not getting enough calories. Get your training and diet sorted first. Don't waste your first cycle just to get what you could easily get naturally.
Take a look in the diet and training forums and put aside thoughts of exogenous testosterone.