Stepping away from your norms and finding a new center of gravity can sometimes be painful.
That pain is a part of growth.
Growth is not always easy and it generally includes discomfort. Being on unfamiliar ground, even within yourself, forces you to find, explore, and except another part of yourself. This process is sometimes painful because you will long for things to go back to what you were familiar and comfortable with. However, the new found journey that you are going through is meant to help you find more of yourself and add onto your happiness.
Growth pains can happen in any situation or level of life whether you are growing within yourself, growing with another person, or growing in expanded consciousness. Instead of trying to search for the why, seek out the meaning of what you are going through and what you are supposed to learn from the journey. Find the positive aspects of your journey and hold onto those as you move forward within yourself and through life.
Being on new territory within your feelings, mind, or environment can make you uneasy because it is something you are not used to. However, embrace that change and know that it is happening for a reason. Believe that the outcome is one that will complete you during the time/level that you are in/on and enjoy the journey so that you can be grateful for it and not reject it.