I used to fantasize about my T telling me that she doesn't ever want to talk to me again. I told my T about my fear of abandoment fantasizes two or three times. She told me that she didn't think that she'd be going anywhere. I would suggest writing a letter to T and/or Pdoc and sharing it in session. (I express my emotions best in the written word. This suggestion is that you use the method that you are best at expressing yourself.) Then talk to T about it. T/Pdoc can't promise to never leave you but they can assure you that they care and let you know that they will let you know in advance if they need to take time off.
My parents got divorced when I was three and I felt like I had to compete with the horses to get my mom and step-father's attention. As you can see, my fear of abandonment comes from my childhood. It might also help you to explore what it is that causes or produces the feelings.
Also, my T reminded me that my friends and family members will stay by my side. I hope that you have parents/siblings/a spouse/a significant other/friend/fellow church member/etc that will be able to stick by you through thick and thin. Everyone needs someone that they can trust to stay with them through the tough times. So, it is only natural that we develop a strong connection or bond with our Ts and want them to stay with us through the hard times.