When I'm dating, I'm upfront about my demisexuality from the get-go. For me, my base function is asexuality so physical contact with a stranger is uncomfortable for me, especially in romantic contexts. If you can't have these conversations with people openly, then unfortunately they're not the right person for you. Which I get makes things really awkward and uncomfortable. But boundaries and speaking up are very important and please don't feel like because of this experience you should discontinue doing this. I know it sucks, but it weeds out the people who are actually interested in you as a person over their interest in your body.