You know I have the same problem and I'm 22 and married. I don't believe it's left over teen hormones either since this is a pretty regular issue and my hormones are pretty steady.
What typically happens is my wife likes sex ~once a week, we then have sex after finishing (and sad to say but the first time around I'm a rather quick shot, maybe 10minutes
), I get more horny, I go into the other room and masturbate. After that I turn on porn and masturbate again. In a night this can go anywhere from 3-5 times after that if I'm still horny I feel the sensation screaming "masturbate" all night long. IIRC it's a gas that fills up your penis with very common compounds to laughing gas.
Anywho, sometimes we'll have sex all week (let me mention THIS IS RARE). Typically we will have sex once a week and then the next two days I'm raging, after that it fades away at an accelerated rate and I'm typically no longer interested. I can go like this, well for a long time with 0 interest.
I mean this is common and has been pretty steady like this for 4 years. I had the teenage hormons from 13 to ~18ish with a few interment spots after that (unexplainable random hard-ons). But I really do not get those at all anymore (aka I have no idea when the last was).