Why do i miss my boyfriend so much?

im 22 and currently living away from home as i am at uni. my bf is at home in NI and i am in Scotland....we have been goin out 2 years! he usually flies ova every other wknd but i jus miss him so much when he not here!! i do live wif a family member which makes things easier but its just nt da same as havin him around!! i cry my eyes out when eva he leave an i hate the pressure tht this must put on him because i no he hates cin me cry and bein upset!! ny ideas on hw i cld make myself feel better wld b much appreciated!! thank you xxx