Why do I cry when my boyfriend leaves me

Keisha • I am 27years old Snapchat: keishahardy1997 I don’t have the premium account

My boyfriend and I have been dating for a month and when he stays the night with me or takes me home after I stay the night with him I end crying every time he leaves and I don’t know why... but when I stay the night with him sometimes it’s on the days he has to work yet I don’t cry when he leaves for work