I would pick one. Either gain weight and stop running so much, or keep running and give up trying to gain weight. If you eat gobs and gobs of food you might be able to sustain a slow rate of gain--a pound a month sounds fine--but why would you expect significant mass gains if you're undermining them three times a week?
I might even back off to three days of weight training instead of four. Many mass gain protocols involve a lot less activity (just short, intense, heavy lifting) and a lot more rest and eating.