How many calories do i need daily to gain some weight back.?

Im 18 male 5'9" I started a couple months ago at 160 pounds did a workout program called insanity went down to 140 felt great. I wanted to get some muscle so i started p90x with some insanity workouts in there but anyway im still losing weight and i dont want to. Im at around 135-136 right now and i want back up to 140. I know muscle ways more then fat and in p90x you do lifting a lot but im still losing weight so it must be my diet. I dont count calories i just eat healthy. So how much calories do i have to eat t gain some weight back but still lose fat?