Age gap

I have posted something similar before on here. But just feel I need to understand why I feel like I do
My husband is 79 in September and I am 63. Both my daughters live in U.S and OZ with my 4 grandchildren
I am feeling very lonely, I do go to the gym and do ballroom dancing and yoga. We both don't have a very good social life with other couples, but I tend to socialise on my own as my husband has no friends.
I work just 15 hours per week, so unless I keep myself busy outside of the house ie shopping or gym, I am at home with him 24/7 and get so fidgety, as I am bored
There is only so much conversation you can have
We went on a months cruise and it was the same, except we saw a lot of lovely places
I appreciate that I married a man 21 years ago, 15 years older than me and now I can feel the difference catching up.
There has been no intimacy between us for over 3 years and I am afraid to say, I miss sex so much. We are more like friends than husband and wife.
I can't explain to my daughters how I feel, as they live abroad.
I feel so unhappy, that sometimes my heart aches and I could just burst out crying