My advice would be never confess! I am not sure what business of someone else's it is, anyway. Once you actually make a commitment the important thing is what you do going forward, not what you've done in the past.
I hate those questions. I've had guys beat around the bush (pun intended!) to get my 'number' and I just laugh it off. I am a confident sexually active woman who is always safe, and that's all they need to know.
Notice I'm single...oh well!