why do i feel like this

so i’m 17 and i was away with my family for three days (except my older sister who is 19 and had to stay home as she has work), i came back with my boyfriend as we have a friends birthday we’re celebrating. i’m staying at home with my sister and ever since i got back from being away from my family (it’s been like two days) i’ve felt really lonely and just wanna be with my mum and see her, i don’t wanna be left alone as i’ll feel really lonely, and have been crying because i just miss my mum being around. i’ve never felt like this before and have stayed at home with my sister while my family were away before and haven’t felt like this. why do i feel like this and how can i make myself feel happier. i won’t be seeing my mum for around another 2-3 days