separation anxiety

from Friday-Sunday, me and my boyfriend spend the weekend together, usually at his house because there is no space in mine. however, upon coming home to my own house, I start to feel anxiety from being away from him setting in. the first time I experienced this feeling, I cried the remainder of the day, couldnt eat because of nauseua, and contemplated harming myself which I havent thought of doing in months. the second time it happened (this sunday past) I felt the same but less severe - I didnt cry nor did I contemplate harming, but I couldnt eat and I did feel extremely anxious. I was able to calm myself down which I couldnt do last week, though it did take a bit of time to do so. overall, my question is, what do you think i can do to prevent this feeling before it even happens (hard to answer, I know). I believe I know why it happens (hes become a sole source of happiness due to being my only social contact bc of covid) but I want to know how I can stop this feeling. anything even comforting words, will be of help :)