I made a song in fl, but it turned out way too quiet. But when I try to amplify it, it clips, even though it is still very quiet. I don't know how to describe it, it just clips even though it's not loud. Is there any way to amplify it without having it clip?

in audacity(if you have it)I amplify and it doesn't clip..although on one song it did.
but what I did was drag the song way out then amplify then clip it back down to the wanted length

I think you can do that in FL not positive though

Use a compressor.

If the entire track is quiet, I'd suggest you apply FL Multiband Compressor to the master track.  If you don't know how to tweak a mbcomp properly, I would recommend the "Warmify" or any of the mastering presets, but it really depends track to track on how it should be setup.

Also look for spikes or clicks in the audio file , transient needles on edit points. Use a pencil to redraw the wave.
In addition to avinashv compressor mabe look at a limiter 2
 

Use another program.
A friend of mine kept on saying I should use Cubase, I also felt at the time that FL, though 'accessible' still sounded 'muffled' and there was the clipping just when it got good!
Why don't you 'master' it in an Audio Editing program? you could export your low volume original from FL and then beef it up in a proper audio editor.

 'Normalizing' the whole track in your editor could bring up the volume without FLs clipping.

You could go the whole hog and export each individual track you created in FL, import them into an Editor like Audacity where you can 'master/produce' the whole song to a much better sound quality.

double the track,  leave one like it is,  add a compressor to the other track set the threshold level to the point where you are getting a -3 -5 db clamp. set the attack to around 10 ms .. listen carefully though cause you don't want it to fast or to slow . Then bring up the make up gain on the compressor to whatever the amount the clamping shows .  Sent them both to a group track or master track..

What this does  is keep the dynamic of the original track and The compressed track with smooth out the peaks and bring up the softer parts. giving you the ability to bring up the gain some without clipping The double track gives more signal to the output .

Thanks for the tip TG... this is a really old (last year) thread, but I'm glad you posted.  I'm going to try your suggestion in some of my recordings to see what it does.
I usually just create an uncompressed stereo mix (maybe each of the individual tracks have had specific compression applied) with an output peaking at -1dB; once I have the stereo mix I work on that in a separate program to get the overall sound I want - this usually involves more compression and sometimes a tiny bit of reverb.

As far as the original problem (posted by Backwards Hat) - my guess is that the individual tracks were hitting the output bus at too high a level - certainly in Cubase I limit each track to -3db max giving enough head room to tweak it, and allowing for any VST effects to change the signal while staying below a level that may clip.  I guess mixing in FL will be fairly similar, but my experience of the software is limited.

Its called COMPRESSION.....my freind..there are a bunch out there
 

btw...good idea goat!