when do I see a doctor?

Kelsey
I'm pregnant, btw. Going on my third week of what I believe to be bronchitis. The past two nights I thought it was getting better, just to have it hit me all over again really bad tonight. 
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Iv had a Bad/deep cough that has been persistent for about 2 weeks, worse when I lay down, lots of green phlegm. Iv coughed so much my throat HURTS, BAD. I feel like I am drowning. Also Green snot and lots of it.
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I spoke to my OB and they said take Robitussin DM until it goes away, other than that, "ride it out"... the Robitussin isn't working, it only makes me feel dizzy and high, and I feel as if Iv taken way too much Tylenol over these past few days. 
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It's becoming increasingly hard to sleep, and even breathe. The coughing has made me throw up multiple times as well. This is miserable. What should I do? Is it serious enough to take an ER trip?