Long Distance Relationship Overwhelm

I am in a long distance relationship and due to the covid pandemic my partner and I will not be able to see each other for a while. Even though we speak everyday and he tried his best to emotionally reassure me, I find that my mind keeps swinging from understanding and being emotionally balance all the way to feeling insecure and having different floods of emotion about different things (but deep down all the flurry of thoughts have to do with being apart) Im struggling to point my finger on the thoughts driving the feelings, they seem to keep changing. I would greatly appreciate if anyone can help me identify how I can better manage my mind and understand how to dive into the thought work so I can pinpoint whether its just thoughts or beliefs or what. Thank you.