“I'm so scared of losing him.” - This is the key problem.

Here is the fact, the more you wanna grab or hold him, the more you are gonna lose him.

A healthy relationship is - we are equally important to each other - "losing you is my loss, and I believe losing me is your loss, as well."

Be yourself, love, and respect yourself FIRST, love him the way he needs, then you don't need to worry about his departure, because leaving you will be his biggest loss.

Best wishes!