Constantly Sounding Congested?

I'm a 15 year old boy and I've noticed that as I'm growing up my voice has grown to just be constantly stuffed sounding. It doesnt necessarily sound nasally, but more just like I have a bad cold. Even when my nose is perfectly clear this still happens. I don't think I have a deviated septum because my nose looks perfectly straight on the inside. I was wondering if its possible that i grew up with slightly enlarged adenoids. I don't think that i have chronic sinusitis because I don't always have cold like symptoms or a runny nose, just the voice thing. Please help me out if you can, thank you