Getting less and less ?

I am with my boyfriend for 2 years.He is 35 and has never been very active in bed,only on holidays,like we had 2 times a day!!Back home normally once a week.In the last 7 month its getting once a month.He says he is tired,and have other thing in his mind,and just forgets about .As I said,he never really was interested in at the beginning of our relationship either.However he is great with cuddling and holding hands.He never liked watching ,or talk dirty etc..I know he does love love me and no other woman envolved and he plans to have a family together and spend the rest of our life together.I am just thinking he doesnt fancy my apperance anymore.I put on 1 stone recently.Him also,but it doesnt bother me.Is it really me, or he become impotence or just just has a low drive?He does have though,just doesnt always ***.Please can someone answer me with similar problem.Many thanks.