my lst child leaving the nest

In the middle of my stressful life my 19 yr old son tole me to causally that he would be living on campus come dec. I acted like it was cool but went to my room and sobbed like a baby. He's my last child. My only son. I lost a daughter in 02' and was astranged from my oldest till just a few years ago. Their father took my girls when they were 13yrs old and they never came back. the courts said they could make up their own close no I did not see or her from them as my ex moved them from state to state as soon as I found them. when Lori passed away in 02' Kerri and I came together and are very close now but she has a mind of her own and doesn't stay in one place long. So to hear I will be losing my Austin in a few short months is the hardest thing I will ever have to face. I suffer depression and anxiety so its going to tough. I knew the day was coming but my heart aches so much already. I know I have to let go but he's my baby. The one that stayed by my side when I was sick and the one who liked hanging out with me on occasions. I feel so lost and sick inside. I know I am being a baby and I will suck it up and deal with it when the time comes. at least I have now.