Not having sex as often is normall?????

My BF of 16 months is not as interested in sex as he used to be wen be began having sex after 4 months of relationship... In d beginning He'd want it almost every day n now its like once in 2 months...
we dont liv together n wen ever we meet I am ok wid just spending time wid him but as Im getting involved with him more(emotionally) my urge for makin luv is increasin n he simply will give sum reason for not doin it.... I settled wid dat may b hez bein a normal guy(getting bored after sum time) but he wont even express anyything abt our physical intimacy(like being romantic) in any way.... he'll seem as if not interested in sex anymore n so I've becum a bit inert n den all of a sudden he mite want to make luv after a month or 2 n i get shocked dat how cum hez still into dis sex thing so im unable to respond or enjoy those moments.. help.......