I almost always have a phlegm thing going on. I have to cough it up or I feel paranoid that I'm going to suffocate or drown or something. Especially when I'm biking uphill. So, my question is, is it better to swallow phlegm, or spit it out? Will it make it worse if I always spit it out, and can my body process phlegm when I swallow it? (I'm not sure that when I swallow it I don't have to just hack it back up again). Also, is there a reason why I might have an over-active phlegm-factory?
It isn't totally clear to me what is happening with you feeling like you have too much phlegm, particularly with exercise--it is possible you are experiencing exercise-induced asthma, which can give the feeling of mucus in the chest with cough, but is more bronchospasm of the larger airways.
It could be allergy related mucus production, resulting in an over-abundance of phlegm in your throat from mucus in your nasosinus area draining down, making you feel you need to cough it up.
So beyond the question of what to do with the phlegm while it is bothering you, is how to prevent it? you might want to try a loratidine tablet (antihistamine that is over the counter) or have an evaluation to rule out asthma.
It is no problem swallowing mucus/phlegm. It happens all the time unconsciously, and is simply protein that is digested--no, it doesn't end up making things worse, and doesn't come back up again. So you don't need to be distracted by spitting it out.