Why does my boyfriend flirt?

me and my boyfrd share a very romantic intimate unconditional love wid each othr.. he loves me so much , i do too. bt i find him lil flirting with gals in facbuk chat? wen i see those chat i cud hardly resist thm..i get soo much of unkwn msgs nd calls to my num bt i don evn respond dem fr the sake ofmy bf ,he s possesve on me..he evn restrictd me frm facbuk nd i evn said ok fr him ..but he in fb goes nd starts converstion wid gals..i m nt lykin it..is tht normal chacrtr of boys ?lyk he doesnt cross tht limit..he s faithful to me but this lil flirtin is hurtin me so much..wat shud i do