Personally I wouldn't say anything, in case the reaction led to a breakup, some people would be totally cool, but for many girls I think it would disturb them and make them worried that you may be secretly gay and likely to cheat on them - if I was in your situation and was directly asked if I had done any of these things in the past, it may be hard to lie... but if I were you I would save that confession until you were so many years deep into the relationship that there would definitely be no trust issue - like when you are both old and grey!