>>81717193 (OP)It depends on one crucial thing
Did you perform the sex act once or more than once?
If once, it's reasonable to say that you tried something, you didn't like it, you decided you wouldn't do it again with that parnter or anyone else.
If you performed the sex act several times with a previous partner, it makes the dude think that you find him less desirable than your previous partner. Clearly, you didn't like it previously but you did it either because you derived some kind of pleasure from your ex doing it to you or that it was very important for you to ensure that your ex-partner found you sexually desirable. It's particularly hard to explain if you did it for more than one partner, unless you accept that you don't like your current boyfriend enough to do it.
Men want to feel desirable. They want being with them to feel special, to be the best you've had. You don't have to tell them this, you just don't have to talk about other dudes in a way that makes your current man think about how these gymbros might've made you squirt.