Sex is a very personal decision and everyone feels differently about it. Some people wait until marriage before they even kiss, let alone have sex. Others are very free with their sexuality and sleep with many, many people. Most people seem to fall somewhere between the two. Regardless of where one falls in the spectrum their approach isn't "right" or "wrong;" it's simply what works for them, and that's okay. To you sex and love are something sacred, and that's what works for you. To others it may not be, but that doesn't mean they are wrong, they just see it differently than you.

If hearing about your boyfriend's previous exploits bothers you I would suggest being honest with him about it. However, I would suggest thinking about how to phrase it before talking to him. For example, outright telling him "It makes me sick that you've slept with so many people" is not an approach that will nurture your relationship. Instead take away the judgment of him and make it about your feelings. Let him know it makes you uncomfortable and hurts your feelings when he talks about other sexual experiences to you. Hopefully he will understand why talking about sex with someone else to his current girlfriend may be upsetting. By expressing it that way, you respect the both of you and have a conversation that can further your relationship rather than tear it down.