My recommendation is to increase your caloric intake on everything, not just protein, but eat clean. Try an additional 500 calories first. If that doesn't work after 2 weeks, add another 500 (If it's an issue, it's easier to drink calories through protein shakes that to eat them). Also, start doing full body routines with deadlifts, bench presses and squats to start three times a week. Keep your reps low and your weight high, but stay within your limits and your ability. (If this is new for you, start with high reps of 8 or more and low weight, then as you begin to adapt to the movement, start introducing lower reps and more weight. Just keep your ego in check by staying within your limits.) Stay away from isolation exercises like bicep curls. They will do very little for you. Also, I would recommend cutting back on the long distant running and try interval training with sprints a couple of times a week. Also, remember to warm-up before hand and stretch well afterwards. You'll put on some size, I assure you.