UPD: I think that you both need to see a sex therapist or something like that. Counseling should help. Usually, the problem is in your head. The anxiety is a very big problem, it just doesn't let you focus on that, because you have too many worries. You need to calm down, talk to each other, try...
It's often linked to relationship issues, stress or tiredness, but can be a sign of an underlying medical problem, such as reduced hormone levels. Everyone's sex drive is different and there's no such thing as a "normal" libido. But if you find your lack of desire for sex is distressing or it's...