JFC.
This thread is a mess.
To PPs:
How exactly does someone "modify" their libido?
Also, no one is entitled to sex.
Further, it is not a basic need. You will die without food. You will NOT die without sex.
OP, you can't diminish your level of responsibility by using "FWB". Regardless of how you dress it up, you are having an affair.
The situation is shit, and your DH is an arse for not discussing it with you. However, that doesn't give you the moral high ground here.
Your marriage is crap - falling apart before it's even really begun. He won't or can't fulfill you either sexually or emotionally (because let's face it, your self esteem will be suffering and you probably don't feel all that desirable, causing you to seek external satisfaction with OM), you're shagging someone else without his knowledge or agreement, and neither of you are communicating honestly.
Whether he has married you under false pretences or not, you have the opportunity to do the right thing: tell him about your affair and give him the option to leave, or tell him and leave yourself, and find someone you are actually compatible with.
Marriage is built on love, trust and communication. You're knowingly hurting each other which doesn't sound much like love, you're cheating so he blatantly can't trust you, and there is no communication.
What exactly do either of you get out of this sham?