Hm.... perhaps the suggestion by "Cuck and loving it" that your woman doesn't want you kissing and sucking her pussy because she's afraid you'll taste the cum of another lover she's taken is a good one.
You might consider initiating a game in which you confess to her you're really turned on by the fantasy that she has such a strong sex drive she can't resist taking other men. Try to set up the game such that whenever the two of you are alone together, she pretends to be your cuckoldress, you pretend to be her cuckold, and she teases you about the man with a big cock she just had that day who is far superior in bed. Your role would be to pretend to be humiliated. As your game proceeds, get more and more into it. Play your role skillfully in ways that appeal to your woman, and encourage her to play her role in ways that play into your cuckold fantasy and turn you on — which could include her denying you (as she's doing, at least partially, already), but in your game she would taunt and tease you about it.
As time passes, it may become gradually harder to discern whether she is playing your game or teasing you about a for-real other lover
she has taken. Eventually you may come to realize, and she may come to accept, that you are in fact her cuckold — and your fantasy will be realized.