How can I confront him if I think he's cheating?

I'm really hurt that the guy I'm dating might be sleeping with someone else. We've been dating for 8 months now. While things seem to be exclusive with us, we haven't had the exclusivity talk. That's the only reason I'm not sure if it would be considered cheating, but I feel like dating for this amount of time has to count for something. There haven't noticed any emotional changes with him, if anything he's more affectionate and sweet. No odd behavior, really. One thing he does that sometimes bothers me is that he'll be "out with the guys" and will text me to check in (say hi, see how my day was/night is and what I'm up to). I'll reply and it will take him ages to get back to me. It's not like I'm checking up on him- I don't want to be that girl that constantly checks in during guys night out. We go out a few times a week, I always stay over at his place. I know this doesn't mean much, if a guy is going to cheat, he will find a way. I like to think he is a fairly honest, good guy. The only "proof" I have is that he keeps box of condoms in his nightstand. We used to use these before I went on the pill. The other day, I went to grab something from this drawer and noticed that the condom stash was a couple of condoms short. My heart sunk when I saw this. I don't even know if I have the right to be upset about this, being that the talk hasn't been had. Again though, we have been dating for a fair amount of time and it's not like it's too soon. I really need some advice on how to approach this-

A) actually bringing up the whole "what are we doing/are you seeing and sleeping with other people" talk. I've never had to initiate this before and I don't care who it's with, it scares me!

B) confronting him on possible sleepovers with others. I don't know if my proof is solid enough to accuse.

Sorry this is so long. I'm really sad about this and It helps to even type it out! Thanks for reading and I look forward to your bits of advice.

OOPS! One more thing: he doesn't run and hide whenever he gets a text or phone call. He will actually say out loud who is texting him and what they are texting about. Over compensation for something?
How can I confront him if I think he's cheating?
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