"Is that fear valid or is it just my past that's haunting me?"
Unless you've got solid evidence that something is taking place, then you're over interpreting the situation because of past conditioning. Try to give him the benefit of the doubt for now. Even if you worry and experience anxiety, this in itself will not change what he is doing(if he was doing it)
Since you're quite aware of what is taking place within you mentally and emotionally, it would be best to redirect that energy onto changing your perception of the situation. How you feel largely depends on what you tell yourself and what you believe. In a way, you may be sabotaging this relationship because of the past baggage that you are still carrying on. In any solid relationship, trust is very important.
When the Past Is Present: Healing the Emotional Wounds that Sabotage our Relationships by David Richo (Paperback)
I see what your saying. I guess its not him cheating on me that I fear, but more that he's avoiding me or trying to slowly or fast, whichever, cut ties and break up with me. Even though to anyone else its a stretch, because of what I experienced it makes me nervous.
So right now, I feel like I'm just waiting. If he responds back it will calm my nerves, and then if he doesn't I'll just feel worse. I know there could be a million possibilities like his phone is not receiving my message or he's busy, etc. I just hope that there is a way for me to get over my fear and maintain a relationship with someone who is pretty easy going. I feel like all this fear and panic happens in the background and he doesn't even know it. I consult my friends and pray and yet my fear is still there.
"If he responds back it will calm my nerves, and then if he doesn't I'll just feel worse."
Being able to control your emotions and not let them depend on others behavior/external circumstances takes practice. You can eventually get to that point and be able to manage your anxiety and worrisome nature (as long as you work on it). While he is away, try to do something special for yourself- meet with friends, go shopping, get your nails done, etc. Taking your mind off of the things that are anxiety provoking is the beginning of learning how to manage your own thoughts and subsequent emotions.