I hear you. There have been many times when I've felt this way too. , Fortunately I've been able to rethink my feelings of loneliness. My T told me to try to realize what a blessing it is to have your own life, make your own decisions,etc. After a while it had the effect of making me attractive again and I think it gives me a stronger position in my relationship with my wife. I actually want a vacation by myself and insist on it which stresses her abandonment issues. I promise to call her twice a day and also have a time away with her as well, but it is important to reserve at least part of my life for me. This will be my 3rd year doing this, and I've experienced good personal growth each time I set out on my own. I rarely feel the loneliness anymore, and I think its helped her as well.
Plus I must add the obvious. There is so much love, empathy, and strength on this website for us all that I have much more faith in human nature than I used to. I hope you feel stronger soon.