Yes definitely post cum would lead to pregnancy as that would be the remains of the semen you ejaculated that gets left in the urethra.
If you masturbate too often, it's possible that you are not waiting enough or aren't getting, let's say it, turned on enough.
I would suggest you to watch a porn video, or some porn videos that you know you really like, and try not to touch for, say, 20 minutes.
If videos really get you excited, you'll probably start generating precum, which, among other things, will act as a natural lubricant.