How do you control lust and become productive?

On the positive side, I have so far been pretty good at keeping myself clean from pornography. Also, my attraction towards real life women (which I kinda lacked while PMOing so much) has returned (or appeared for the first time I'm not even sure anymore) and I'm very happy about it. But there are a few other problems that this has led to...

While I avoid porn completely and sexually suggestive media as much as possible, my mind has created a mechanism to fantasize over women (usually of my personal preference) a lot. This has led to what I would consider a somewhat serious and intrusive problem in my life in which I started masturbating in own bedroom while doing work, which usually wastes a lot of time and energy. Because of it becoming so much of a problem and me starting to notice how much it clogs up my mind and messes up my work routine, I've resorted to just MOing (without porn) just to release the sexual tension I have built up. The problem is, this only leads to me desiring it and lusting in my mind even more afterwards, and is merely a temporary fix (although I don't feel that guilty about it anymore, which lessens its negative aftereffects). Are there any ways that I can transform this built up sexual energy and tension into something more productive than masturbating and orgasming? Any help would be appreciated because I got an exam coming up soon and I need to focus my mind again.

 

Thanks man, I appreciate the advice! Although I don't have the means to get to a gym right now I'll try exercising inside and outside (despite the weather) as much as possible! I gotta get my life back in order!