There's a number of options to choose from:
He's gay
He's got a low libido - with a possible underlying medical cause that could be resolved
He's getting it elsewhere
And, fwiw, my money's on him being a self-control freak and he's deliberately withholding sex because he can - and he may be doing it to punish you.
For what exactly, who knows? Maybe because you expressed your dissatisfaction with him being a workaholic or some other utterance that he took against because it upset his view of how he perceives the world.
If this is the case, all the tarting yourself up in the world and wiggling your bum like Jessica Rabbit isn't going to tempt him as he'll get off on not being tempted - and on making sure you literally won't get a rise out of his dick him.
If I'm right, you're best advised to sit him down and coolly explain that as he is unwilling to fulfil his part of the marriage contract and worship you with his body satisfy your reasonable sexual needs, you see no alternative but to take a lover.
In the same neutral and unruffled tone, assure him that this will in no way affect the smooth running of his household and, as you will of course be discreet, no gossip will attach to your joint good names and standing in the community.
Tell him your love for him is undiminished and, as he is the only man you will ever love*, he need have no fear that you'll fall head over heels for another.
Give it a couple of weeks and then start walking around with a smug smile on your face (you may need buy in a rabbit or 2 to make your chops look realistically like you're getting it somewhere the cat that's had the cream)
*I know it's pass the sick bucket stuff but needs must when you've still got an itch that needs scratching the devil drives.