What you're experiencing is not an overactive libido but insecurity. You've mistakenly equated sex with acceptance and permanence. That has, in all probability, resulted in his perceiving you as clingy and demanding. That'll prove toxic to most any relationship, because it is natural for adults, men particularly, to feel the need to pull away. We feel smothered, in other words.
Your best bet is to back off. It might not hurt to go for some professional counselling, but until you do, consider a few pertinent facts.
As we age, we men find our sex drive diminishes. We find that increasing demands at work and at home require larger expenditures of physical and emotional energy while leaving less and less time for recovery. That's why so many 30-something males are turning up at the doctor's with stress-related illnesses like cardiovascular disease and irritable bowel syndrome, and why so many of us are dying of heart disease in our forties.
In one of nature's worst ironic twists, most women, once the necessity for concern over pregnancy is gone, experience a surge in their sex drive.
It matters little whether that which negates concern for pregnancy is the onset of menopause or due to a surgical procedure such as tubal ligation - women tend to feel suddenly free and able to fully enjoy nature's gracious physical endowments.
In other words, now she's the one who's hot to trot at the same time he - justifiably - is beginning to say "Not tonight, dear, I have a headache". This is a heartbreakingly common experience for men and women in their forties. It's a period when men experience the highest job-related stress of their entire careers, accompanied by the acute stress of struggling to parent older adolescents and children reaching the age where they leave home for college, marriage, the military...
It is NOT an ideal time for most men - and by extension, for most women, who undergo much the same stresses. At this time in a relationship, if either partner comes across as being more demanding, and crankier when those demands aren't met, the results can spell real trouble. It can, in fact, spell disaster. She gets so frustrated she starts thinking up ways to get even, while he begins to wonder what the he*ll he ever saw in marriage in the first blasted place. He begins to look for a way out while she looks for a way to hit him hard with how neglected she feels.
He may boogie on outa here on a motorcycle, carrying a far less demanding floozie on the back of the bike (though often as not, he's alone) while she deliberately leaves unmistakable evidence of a torrid affair with the friggin' gardner lying about for hubby to find.
Not in every case, but you should get the idea by now. Failing to deal with your dissatisfaction in a rational, adult, and yes, loving manner is fatal to a relationship. If the relationship once mattered, you need to decide whether it still does, and take the appropriate steps, starting with counselling. If he won't go, go yourself; you'll still gain valuable insight into the situation. Get a wiggle on, sugar, time's a'wasting!