Firstly, is it just how your vox sounds to you or are you having difficulty combining singing and playing?
If it is the former, then yes, singing lessons may help you get much more out of your vox! "Your" underlined because if you really can't sing, nothing will turn you into the next Pavarotti - PROBABLY! BUT, singing lessons will enable you to get the most out of what you've got.
If it is combining singing and playing and having difficulty with this, the only thing you can do is practice; practice and follow a couple of steps - when you perform a song, you usually start playing the guitar before you sing; when you sing try to hold both the rhythm of the song and the true melody with your vox and follow this with the guitar. The reasoning behind this is that most people's ears tune into the vox and will follow lyrics as long as they are sung true and in rhythm; once the performance of the lyrics is mastered, it stands as a guide for the accompanyment (the greatest accompanyists follow what the vocalist is doing anyway!)
To this end, it serves to spend time practicing lyrics unaccompanied.
I hope this answers your questions or gets you on the way to the answers you require. If you need more info, please get back and someone will be able to help!
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