leaving anxiety

so every time i'm with my boyfriend and one of us is about to leave, i get like super clingy. i'm ok being away from him for periods of time, it's just when we're leaving i don't want to let go. when i left for college, i just was painfully alone and my first semester of college was just a really sad time for me, but every time he's about to go i get super emotional and like really anxious about being by myself. like after sometime has gone by I'm ok, I actually don't mind spending time alone, I like giving him a little time to miss me. i sort of get that feeling with everyone, with my best friend it isn't so bad but for most of our relationship she lives in another state so i often went months without seeing her so i was ok, there was also a time when my mom was taking care of my grandma because she was sick so for months i was living with a friend because my mom was never home so i was also used to going a long time without seeing her too. but ever since my boyfriend and i started dating we didn't go more than a week without seeing each other so i think with him it was the worst. it's like every time he has to leave a twinge of that fear of not having anyone and just being all alone comes back to me. i think he's starting to notice, like before he kind of just looked past it but he's starting to notice and i don't really know how or if i should even bother bringing it up. i kinda feel silly that i can't say bye without feeling emotional