Does sound like sub drop to me, possibly combined with some feeling of lack of affection afterwards and missing the sensation of vaginal sex. In terms of sensual feelings and also emotional facets of sex, vaginal sex and clitoral sex are different and if you don't get one you can miss it (so I have been told). I know this because at least one woman I have been with has never been satisfied with 'mere' clitoral orgasm. Once she has had that orgasm she then needs to be penetrated, if only for a short time, in order to complete the 'sexual experience'. She doesn't even need to orgasm from this. just feel something inside her.

Maybe you could ask your Master nicely if he wouldn't mind using a dildo on you when you are allowed to cum, or maybe just plugging your vagina with something? Its an extra level of humiliation/sensation as well as fulfilling this need of yours. You should also, more importantly, look to aftercare and make sure that you get hugs and so on when you get these 'special' sessions as well as after vanilla sex. A chance to talk about the experience with him openly and frankly is also a good thing to have.

And never worry about talking about such things on here. While no one may have had the exact experience you have had I can bet that all of us have had similar ones which are equally likely to make us blush. No one will judge you for something like this.