Just ended my first relationship...

Hey all, I'm 25, and I just ended my first relationship. This guy was the first one I ever really dated beyond a first date, lost my virginity to, etc. I have a few thoughts if anyone has insight on them, because I'm at a loss:1) My ex and I broke up because we (mostly him) felt there wasn't a spark, but we were really close and want to stay good friends. I want to do this, but how can I make sure I do it without blurring the line between friend and boyfriend too much?2) It's only been like 4 days, and I know it takes time, but I feel like I at least start and end my days feeling like I miss him. The romantic desire is gone, but I just miss seeing and talking to him, since we're intentionally taking a week or two for things to settle. Any tips on handling this feeling? (because it really sucks)3) How do I navigate moving forward? Now that I've been sexually active part of me wants to go hook up with guys, but I feel like it won't be fulfilling enough. On the other hand, I crave intimacy but can't imagine myself being intimate with another person now.Thanks to anyone who takes the time to help!