Without having listened to your track: it's not surprising at all it looks this way if this is just a bass-and-drums loop with not changes. How could it look anything but constant-peaks-amplitude, if it is a loop that literally repeats in exactly the same way?
The fact that this constant amplitude is actually 0 dB (i.e. the maximum possible) is just a matter of normalisation. It's standard practice to set the level as high as possible without clipping when exporting audio. Either the compressor plugin is set to normalise the output, or LMMS does that in the bouncing/exporting action.
Even if it wasn't a loop: a compressor has essentially the purpose to bring any audio closer to constant level. This is very often a desired thing, in particular for something like a video soundtrack: if there's lots of dynamic fluctuation, it's much harder to mix it together without the peaks disrupting the voice-over or else the music getting feeble in the background. Of course you will need to properly adjust the mix levels for the video cut, but that needs to be done either way. Your loud music track will probably need to have quite a low mix setting in the video, but that's not a pad thing per se.
Also in music production, especially pop, mastering engineers will often apply so much compression that the peak level across the track is almost constant 0 dB. This way the overall track will sound as loud as physically possible even on small speakers. The downside is that the music isn't as dynamic anymore. This has been a big debate termed the loudness war. But that doesn't really apply for you if you really have just a loop: there are no dynamics in the first place, so also no issue removing them with a compressor!
Bottom line: don't worry about this. You could certainly reduce the output level in LMMS, but if the track doesn't actually sound bad to you then there's no real reason. You should make sure you've actually checked it on studio monitors as well as headphones, to make sure it isn't also clipped after all.