Congratulations on your 5th baby!
By any chance do you have acid reflux? Even if you do not have obvious symptoms (heartburn, a feeling of liquid coming up)there is still a condition called silent reflux and it can get worse with pregnancy. If this is the case, the lump in the throat (fullness) can be caused by irritation coming up into the throat where your vocal cords are. When left untreated it causes your throat to basically swell and close off the section where the acid would come up and possibily get leaked into the lungs. This is the explanation given to me by my Allergist. When left untreated you can also get a fullness in your chest, making it feel as if it's hard to breath. In my case I even have acid reflux induced asthma. You wonder if you're having a heart attack, and you kinda panick over the lump in the throat - tightness in the chest - but then you get checked and your heart is fine :). It can make you anxious and for about a year I had a horrible doctor tell me that I just had anxiety. Well, I did't. I had severe GERD. I knew I had heartburn but was eating tums and taking zantac, I had no idea that it was causing these other symptoms. My first pregnancy I had hearburn but not all the other symptoms (I only ate tums), my second pregnancy brought on the lump in the throat feeling and chest heaviness. I never made the connection but I can remember not being able to bear even wearing a turtleneck, it was as if it was choking me. I also have MVP (mitrovalve prolapse) and I get fluttering and heart palpitations so I thought it was related to that. AFter second baby was born (I did not treat my heartburn, actually I didn't even really think it was an issue this time) the chest heaviness was worse and the throat lump was making me nervous. I had my thyroid checked (that can also cause that feeling) and then finally went to my allergist to get checked for asthma (since I was having the chest problems and it wasn't my heart) and low and beyond, found the answer. Not anxiety, Gerd. I am now pregnant again (#3) but take nexium so it hasn't been an issue. Just get a mild cough from the irritation of the acid coming up when it breaks through...but overall I've got control of it. It took me months of a high dosage of nexium to get rid of the feeling of the lump in the throat and chest heaviness but it definately worked.
Please check with your doctor first about the Thryoid (to rule it out) then ask about acid reflux if having symptoms or silent reflux if not having symptoms. I can remember feeling like I was choking. It's very scary, but if it is from reflux, it's your body's way of trying to keep the acid from going into your lungs which can cause damage. In the meantime, try taking Maalox (safe when pregnant) and see if that helps at all. It tends to coat the throat better then eating tums or taking zantac, which only neutralizes acid but still allows is to come up and cause the throat to swell up that little "v" in there that is trying to protect your lungs.
Take care and good luck with your pregnancy!