As long as you and your husband are both in agreement as to what you are hoping to achieve by entering into a cuckold marriage, it can be beneficial. In the least, you could enjoy a more pleasurable sex life and your husband would enjoy the benefits of having a well satisfied wife and reduced stress if your current lack of sexual fulfillment is causing you to be irritable and he to feel inadequate.
I advise that you take the time to read through the various older threads here to familiarize yourself with some of the basic variations and to get ideas as to how you would like your relationship to work. There is no one right way to do this as there are many different styles of cuckolding and the only right way to do it is the way that works best for you and your husband. That will require a lot of communication between the two of you to determine what your limits are, what responsibilities each of you will have and how you will deal with any issues either of you have as you progress in your exploration of this lifestyle.
Much of what you will read here and on other sites is fantasy based, but there is also some realistic information sprinkled in with it.
However, before you consider making such a radical change in your relationship, if the only problem you have is your husband's lack of size, you might want to explore other avenues by which he can satisfy you such as using various toys such as multiple vibrators, various size dildos and even using a strap-on dildo in place of his penis. Keep in mind that there may be a lot of heavy emotional issues that can come to the surface once you make the decision to try cuckolding and it should not be entered into lightly.
Best wishes.