I really hate seasonal allergies. My ears and sinus cavities are so plugged up, even with meds, saline wash and whatever else I can think of, that I can't hear the pitch of what is coming out of my vocal cords. I'm shocked at what I think sounds sort of acceptable when I'm playing along and singing, but to watch back a recorded video through headphones or larger speakers is shameful. Hopefully this will calm down soon in the Northeast.
One trick I've learned is to use my PitchLab guitar tuner on my Android tablet and phone. It has a continuous chromatic display so you can see the notes you are singing and the notes of the guitar like a strip-recorder (think like an EKG output). I pluck a note on the guitar and then sing what I think I hear. And it is almost always a full step or more off. But the more I go back and forth, the closer I get. Then I just have to memorize how each note feels rather than how it sounds. As I get better I can play and sing along knowing where the voice notes and guitar notes are on the screen. I make minor adjustments to keep in tune as I go along, constantly memorizing the feel of each lyrical phrase. Difficult and time consuming. Got to be a better way.
Maybe I'll just focus on instrumental for awhile and get someone else to sing? Or I'll do a rip of speaking blues videos. Er ,something.
A practical question comes up. When singing in key, which note of the chord do you typically put on the lyric? First, third or fifth? Is there a rule? I find myself naturally singing the third or the root note when in the key of G. My guitars are tuned 151.