Give up on singing

Practice and if you aren't already try to take voice lessons.

I have a similar problem. I can sing really high and then in a lower range. It's the middle stuff that gets me. I'm not a good singer in the first place, but I'd recommend learning a voice exercise. (You might be able to find clips and instructions on the internet.) A regular run of do-re-mi in different octaves is a big help (http://www.ibreathemusic.com/article/44). You can start lower and work your way up. It does get easier, but you have to keep it up, or else it sort of goes away, at least that's what happened to me. I had to practice to get into a higher range. I can still do it, but it's the mid to high range that got harder after I stopped practicing. Unless you're trying to train yourself for classical music, you shouldn't worry too much about it. Singing in an odd range might actually be an advantage if you're a woman in a band. Not many women sing lower, so it could be distinctive for you. Some music, like trip-hop, actually uses breathy voices a lot. You can make it your strength. If you're just singing to sing along, you can harmonize with the music. It's fun to make unexpected harmonies with the music. I hope that helps!

Do crescendos and decrescendos, try to close the gap and smoothen the transition between low, middle, and high, you don't necessarily need a vocal teacher if you are just trying to get the middle voice going, but it is a good thing to have one as long as tthey teach speech level singing... I had the same problem, but I like to do what they call 'belting' so I would start on a low note, and while using diaphragmic breathing slide up slowly to my highest not, and slide down again... where ever the gap was I would work on the most... if you are using mixed voice, then you start on a low now with your chest voice slide up and smoothly try to make it to a note that uses your middle voice, then try to work my way up to a voice that uses my head voice... if you know none of these terms just look it up, it helps understanding what happens when you sing different notes, either way work on you passaggios a lot, to get your higher voice stronger, it depends if you are doing falsetto in the first place or not, if you are its difficult to add much to it, if you are using you chest voice to hit high notes(belting) then work on breathing exercises so that you won't tense up, leaving you with bad technique... sing your own voice, just be yourself when u sing and much should be accomplished with the help of dilligence