Dear billie. You have spent so many years with your husband. You should know him very well by now. You are also the one that understands the situation well. I will be honest and blunt with you.
There could be several reasons for the problem:
1) your husband has a hormonal or psychological problem where he does
not have the urge to make love.
2) he does not find you attractive enough to make love to you.
3) he is secretly involved with another woman but does not want to break
the relationship with you.
Whatever the reason is, this is a serious problem. You cannot go through life making love so infrequently. In general, men want to make love at least once a week especially when they are as young as your husband.
For some like me, once in two days is the frequency.
You need to find out exactly from him what the problem is. Ask him to be straightforward with you about it even though it might hurt you.
If worse comes to worse, you might have to move on to someone who cares enough about you to want to make love to you more often.
One thing is for certain. You are not the one at fault here and you deserve better treatment than this.....