Mucous build up normal?

Hi, all. :)

I've been practcing singing everyday for almost a week, and I've noticed a buildup of more phlegm in my throat than usual. Is this something that is normal? Is my body just getting used to singing everyday, does it mean I am doing something wrong? 

It's very normal to "kick up" extra phlegm when singing! Your vocal folds are vibrating at a very fast rate, and they require fine coordination. Phlegm gets in the way and makes it harder for your folds to come together "cleanly" - so you may notice phlegm more when singing. 

As for increased phlegm production over all, that's more likely to be the result of dehydration (thicker mucus), allergies, postnasal drip, illness, or diet. 

I recommend increasing your water intake, and consider a humidifier or steamer, plus nasal irrigation with a saline sinus rinse like NeilMed. More advice on throat clearing below:

Certain non-verbal vocal behaviors such as chronic throat clearing or coughing are also very hard on the vocal folds and can lead to irritation and injury. Most people with this problem report that they feel a sensation of mucus or a tickle leading them to clear their throat. The throat clear improves the feeling for a short while and then the feeling comes back. In reality, what is happening is a vicious cycle. The throat clear or cough causes as much irritation as it relieves and, in the end, the more one clears their throat, the more one is likely to feel like the need to again. Strategies to help avoid chronic throat clearing include sipping water, using lozenges (avoid menthol or eucalyptus), chewing gum, a rapid exhalation, or a dry swallow. None of these strategies feel as good as a throat clear but they help, and the more one is able to resist that next throat clear, the closer one is to no longer feeling the need to.

Source: https://healthcare.utah.edu/healthfeed/postings/2013/04/041713vocalhealth.php

Hydration is key. Drink water in the hours building up to singing. Avoid milky drinks like tea and coffee. Avoid fizzy drinks too as they can make you burp!

I learnt this the hard way.

Good tips!