“Asexual” as the term is generally used on the Internet generally means someone with no sex drive and no desire to have sex. Often such people want a loving platonic relationship, but without sex. Generally they are able physically to have sex, as in they have all the equipment and physically it works, but according to them they have no desire. I have met some such people.
OP, it doesn’t sound like your husband would be considered “asexual” by members of the asexual community, given that he had sex with you at least on some occasions and he entered into a marriage where the other person (you) expected to have sex. The asexuals I’ve met don’t want to have sex at all, not even twice a year, in many cases not ever, and they aren’t shy about communicating that.
There could be many things going on in your relationship with your husband - a medical issue, a psychological issue, a lack of attraction to you, a lack of attraction to women in general, etc. and you really would need doctors and professional help to sort it all out.
As The Little Lady said, the Church does not dictate how often we have to have sex or what our libido should be. I also would caution you that “normal” for you may not be “normal” for your husband or for anyone else; there are likely people for whom “normal” is 2 or 3 times a day and people for whom “normal” is a couple times a year. We are all different. Libido also can change a lot over time due to age, health, medication etc. and even just due to priorities in life.
The concern here is not what is “normal”, as there are likely women out there who’d be fine and “normal” with twice a year or even not at all, but the fact that you and your husband are mismatched in your expectations of how often you want to have sex, and also you do not at this point understand what’s causing him to act this way and that can cause a lot of insecurity and upset.
I would suggest having a frank talk with your husband, and that he should discuss this with his doctor, and then go from there, depending on the outcome of both.