Yo, man I know it may seem kind of lame, but I'd rock a mask if I were you. Especially if you are painting indoors.
There are horror stories of writers who cough up blood, have frequent migraines, asthma, bladder problems...it's nasty shit...so a cheapo painter's mask for 6$ is worth it. Bandanas and shirts don't keep the fumes all the way out, but they help and it's better than nothing I guess.
If you are really serious about it, a 30$ mask isn't a bad investment all you'll need for the rest of your life is new filters