I was having sex with my boyfriend and I was laying flat on my stomach. I wanted to stop so I said "let's stop" and I pushed myself up on my elbows so I could pull off him. He pushed me back down flat and said he was " not finished" and he was about to reach climax. Then he reached climax with in seconds of pushing me back down. My friends say because he didn't stop when I said "stop", that classifies as rape. My bf told me that he was seconds away from climax (which he was) and wanted to finish because I had reached climax earlier. Is this rape? I am very confused. Should I break up with him? report him? Any suggestions or comments would be greatly appreciated.

I'm having a lot of difficulty comprehending this scenario and wrapping my mind around it.
1) You didn't state your reason for wanting to stop, and it makes no sense to me why anyone would want to stop in the situation you've described, or omit the reason from this thread. As well, you didn't indicate that you related the reason to him at the time. And it seems hard to believe that someone would disappoint their lover in a situation like that without offering them any reason or explanation for wanting to stop.
Additionally, it doesn't make sense that he wouldn't ask you what was wrong. It's like he thought it was the most natural thing in the world for someone to do what you did, and that it's a very common occurrence. And thus he wasn't curious what was wrong, and whether you might have suddenly experienced signs of severe diarrhea and needed to evacuate your bowels immediately to avoid a huge mess, etc.
2) When someone is on top of you while you're on your stomach, it's obviously impossible to "pull" them off of you by propping yourself up on your elbows. And if you were able to prop yourself up on your elbows, that indicates that you had sufficient maneuverability to do so because he didn't have all of his weight on you, or was just straddling you. And if that's the case, you should have been able to immediately "extract" his penis/stop the sex simply by forcibly rolling over onto your back.
As well, if you were able to prop yourself up on your elbows, that means you had full control of your arms and hands, meaning that he wasn't pinning your arms down. Thus you could have easily put your hand around his penis to immediately "circumvent continued penetration."
3) If someone was on top of me engaging in anal intercourse, and for some reason I wanted them to stop immediately, the last thing I would do is prop myself up on my elbows. As that clearly would have zero chances of accomplishing my goal. And in the heat of passion, when someone could be ready to cum at any time, it'd be extremely unrealistic for me to expect them to stop and withdraw instantly just because I said "let's stop." This is a case where actions would clearly speak a lot louder than words, such as me reaching back and putting my hand around his penis to force him to stop even if he didn't want to.
But I don't know, that's just me. Maybe you don't have the boner crushing grip I have. However, most males have a strong enough grip to discourage any erect penis from continuing what it was doing.
4) RE: "He pushed me back down flat and said he was " not finished" and he was about to reach climax. Then he reached climax with in seconds of pushing me back down." This is what I'm having the most difficulty comprehending. You've interrupted whatever fantasizing he had going on in his mind with some extremely negative, self-esteem crushing news. The fact that you wanted to stop. As this is rejection, pure and simple. This guy undoubtedly thinks of himself as a stud, and he's giving you what you obviously wanted at the time you commenced the sex act.
Yet after having his bubble burst and being totally distracted from his fantasy's, he's still so turned on that he's "
able to reach climax in seconds." This just doesn't make sense to me. And you made no mention of him being drunk or drugged, so I have to assume he had all of his senses in play, and thus his brain was able to register the erection killing rejection.
5) If he's your "boyfriend" and you had a sexual relationship with him, why would you be contemplating ruining his life by accusing him of rape and reporting him to the police? Since you were already having sex and he didn't respect your wishes to stop immediately, it sounds like he clearly hurt your feelings and should be dumped for being an inconsiderate jerk. As according to your description, he wasn't even concerned whether you might be experiencing a heart attack or some other medical emergency. But charging him with RAPE? In my opinion, it's totally unrealistic to consider him guilty of rape under the circumstances you've described.