My son has someone else

But why?

But why? Why did I make all those excuses? Why did I argue with him about him moving away? I thought I liked and trusted Estefany with Alan. But why am I starting to change my mind?
To me, Estefany was amazing and an awesome girlfriend to Alan. But the days Alan was mad at me for not wanting him to leave, or the days I saw him sitting at his desk looking for houses on his computer, were the days that made me despise Estefany more... and more. It wasn't Estefany's fault, and I understand that now, but those days I couldn't manage to convince myself that she wasn't the problem. In fact, there was no problem. If there were a problem, the problem would have been me. But back in those days, I thought the problem was Alan leaving. But why?
I thought Alan leaving at 18, almost 19, wasn't the best plan especially since Estefany would turn only 18 in just a few days. I thought it wasn't a good idea because they still didn't have a good image of the real world; they had just turned adults. I just wanted what was best for them. But is that really what I thought? Or is that just what I told Alan? The real reason I didn't want him to leave was because... I would miss him. In my heart I felt like I would die without him by my side. He had been right there.. by my side, for almost 19 years!! That's why I became mad at Estefany, I started to feel like he loved her more than he loved me. One word for that... jealousy.
Was I jealous? Or did I just love him to the point I didn't want him to leave? Was I protecting them from the dangers of the real world at such an early age? Or was I just preventing a great future?