Sounds just like me, for the first 8-9 weeks of my pregnancy I thought I had a cold, went to my doctor and he gave me beconase nasal spray (its a cortico steroid but safe for use in pregnancy. I only used it till my symptoms cleared up and so far I have stayed congestion free.

While it may feel like a cold (mine did), it is actually "allergic rhinitis of pregnancy" and more common than most realise.
It gets to your chest because the mucus is slipping down the back of your throat to your lungs (i had several bad coughing fits which produced loads of mucus from my lungs - nice)

Say that sounds like what I have, I should call my doctor and see if that is what I possibly could have and try and get it cleared up. It really isn't a very fun thing to go through.