Do you mean that you do everything with them? There isn't one event where you have missed? Which one of the two do you like more honestly if you ask yourself?
To stop this, you need to focus on your life and what will help you in future rather than following the two guys like a puppy dog. Its the same idea as a girl stringing along a guy because she just wants fun but always leaves a little behind to make the guy keep coming back.
First ask yourself the simple questions, where you want to be later on in life? What do you want to do? If you do not expand your network or friendships with new people will you be stuck in the same world you are in now?
What you want sometimes may be your brain only seeking the comfort and satisfaction. But what you really want to do with your gut feeling, instinct and heart is reality.