Advice from the old lady:
Talking dirty is really a window into stream of consciousness if that makes sense. You are allowing thoughts about sex, sexuality and erotica to be verbalized in the moment with your partner.
It shows you to be engaged with your partner, which is flattering to your partner.
It is at once candid, hot, and intimate. In the midst of sex it is validating to hear how your partner is aroused and to hear what they desire in a direct unfiltered way. Conversely to NOT do this (particularly if your partner already has) can stymie that flow of intimacy between you, as OP observed.
It doesn't really matter too much what you say...but how you say it and that you are not too self conscious to express naughty, dirty or sexual feedback with your partner.
Being self conscious is a buzz kill for good sex. Don't allow "how silly/stupid/awkward I feel" to block you doing this. That's all BS up in your mind.
As an aside and as to what
@Urbanyst said, communication is extremely important in intimate relations. Doesn't matter if your woman is a virgin or is very experienced. Different things work better for different people. So yes you need to listen to your partner and learn what turns her on or gets her going physically. You can't assume whatever YOU are doing is the best thing to be doing. That is a terribly arrogant stance. You don't live in her body, she does.
Think of it this way. Women don't have man physiology, obviously. How does a woman get good at oral sex? Some man has to teach her/tell her. She can't feel what he feels (she doesn't live in his body) so she has to listen, observe and respond in order to please him. What if you are with a woman who doesn't give good oral sex? Are you going to let her try although it may be uncomfortable and may dampen your arousal? Not if you have any sense...rather you are going to guide her and communicate what you like and what you don't. Women are no different.
If you as a man are unable or unwilling to listen to what your partner needs to enjoy sex, then you are actually stifling your own enjoyment and it's a matter of time before she drops you or starts turning down sex because you are being selfish in bed. You gotta lose the ego and listen to her if she is trying to communicate in this way.
The other thing about dirty talk is that it isn't for public consumption. Meaning it's quite private. So the ability to verbalize the naughty thoughts you have in your mind when you are with your lover builds connection and desire between you. Sometimes it can be very sexy for example to be out somewhere public, and whisper a trigger phrase from talking dirty to your partner. The trigger prompts recall of something sexual between you and creates sexual tension and arousal in the moment (bonus points if you cannot act on the trigger right away). This is sexy, intimate and builds tension. Women love sexual tension. If you learn how to tease and play with dirty talk in the bedroom you can actually bring it outside the bedroom in small doses and effectively create heat and desire elsewhere...and I think you'll like the results.
Contrast is also quite sexy as
@Fruitbat notes. People who appear very buttoned up in public but are uninhibited in bed are intriguing in part because of that contrast between the buttoned up public persona and the private wild side that few see. Again, this build intimacy. Dirty talk is a way toward intimacy. Don't forget that.
