Marriage is an 'agreement' of committment. A 'contract' that you will be faithful, caring and only for one another.
Does it need to be in a church? No. Does it need to be religious at all? No. Does it make it less of a marriage if it is not committed to under the eye of God, and with religious ceremony? No, it does not.
A non-religious marriage is as 'sacred' as a religious one. The ONLY people who should be concerned about it's sacredness, however, are the TWO people in it.
Marriage is between two people. Other people should not enter into someone else's marriage. Other people should not be able to have any say in who one can marry either. They should really look at themselves and think "how would I feel if I was told I could not marry so and so?" before they poke their nose in. A marriage is between the TWO people in it - NO ONE ELSE.
Government and God? Should be, and stay, separate. Government should still give out licences, and if two people want a religious ceremony, God should be invited.
Divorce? I can see it's benefits - for some couples (such as my parents....yes, I am here because of them - but they have found more compatible people! Whew!). But, in my own marriage, I feel it does not have a place.
I believe if there is a God, it's not really the biggest thing on his plate - marriage. I'm sure he's a little busy with natural disaster management, plagues, famine, attempting to re-direct the Westboro Baptisit Church into doing good, smiting a few naughty nasty's, to be overly worried with 'recognising' marriage.
So relax - your marriage is as sacred as you want it to be - whether it's in front of God, or not.